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Home , Carbohydrate metabolism, Gluconeogenesis, Glycogenolysis, Glycolysis, Hepatic fructokinase, Lactase

Wichit Suthammarak – Department of , Faculty of Medicine Siriraj Hospital – Aug 1st and 4th, 2014

• • • synthesis • • pathway • Metabolism of other hexoses Carbohydrate Digestive !

Polysaccharides/complex Salivary glands Oligosaccharides/dextrins

Dextrinase Membrane-bound Microvilli Brush border

Maltase ‘’

2 1 glucose 1 glucose 1 1 Cause & Pathophysiology!

Normal lactose digestion Lactose intolerance Lactose Lactose Lactose Glucose Lactase lactase X Galactose

Bacteria

1 glucose Large 1 galactose Intestine gases, organic acid, Normal stools osmotically Lactase deficiency active molecules

• Primary lactase deficiency: อาการ genetic defect, การสราง lactase ลด ลงเมออายมากขน, พบมากทสด ปวดทอง, ถายเหลว, คลนไสอาเจยนภาย • Secondary lactase deficiency: หลงจากรบประทานอาหารทม lactose acquired/transient เชน small bowel เปนปรมาณมาก เชนนม injury, gastroenteritis, inflammatory bowel disease Absorption of Hexoses Site: duodenum!

Intestinal lumen Membrane Transporter Blood SGLT1: sodium- Na+ Na+ • Presents at the apical membrane of enterocytes SGLT1 Glucose Glucose • Co-transports Na+ and glucose/ Galactose Galactose galactose GLUT2 Fructose Fructose GLUT5 GLUT5 • Transports fructose from the intestinal lumen into enterocytes GLUT2 • At the basal membrane: Glucose! GLUT2 Glucose transports glucose, galactose and fructose from enterocytes Galactose! Galactose into bloodstream Fructose! Fructose GLUT2 • Presents at the apical membrane during high luminal [hexoses] GLUT2 • Transports glucose, galactose, and fructose The is the first stop for the most absorbed from the digestive tract Glucose Uptake at the Peripheral Tissues Glucose transporter- GLUT!

Glucose Glucose transporter (GLUT) Outside plasma membrane

Cytosol Glucose Transport via glucose transporter (GLUT) • GLUT: transmembrane on the plasma membrane • Facilitated passive transport (no ATP required, downhill, carrier) • Conformational change Glucose Transporter

Transporter Tissue(s) Role GLUT1 Ubiquitous Basal glucose uptake (every ) Endothelial cells of the Transport glucose from blood-brain barrier blood to CSF

GLUT2 Liver, pancreas, intesne Remove of excess glucose from blood GLUT3 Neuron Basal glucose uptake (neurons) GLUT4 Muscle, fat, heart Acvity increased by GLUT5 Intesne, tess, , Primarily fructose sperm transport GLUT6 - GLUT12 Others Currently being studied GLUT4 Insulin-responsive glucose transporter!

GLUT4

• Myocytes, , • Insulin-responsive GLUT o Increases glucose uptake up to 15X • Some SCL2A4 have been found to be associated with mellitus (DM)

Regulation of glucose transport by insulin-responsive GLUT4 (Lehninger Principle of Biochemistry, 4th edition) Kinetics of Glucose Uptake via GLUT Characteristic of GLUT1 vs GLUT2!

Vmax

Normal plasma ½ Vmax [glucose] 0 = 80 - 110 mg/dl (4.5 - 6 mM) entry, V (uM/min) entry,

Initial velocity of glucose Kt Extracellular [glucose] (mM)

GLUT1 GLUT2 • Every tissue • , , pancreatic islet

• Kt of glucose ≈ 1.5 mM • Kt of glucose ≈ 66 mM • Basal glucose uptake • Control plasma glucose Major Pathways of Glucose Utilizations

Extracellular matrix and cell wall Glycogen,

synthesis of storage; structural polymer ‘Glycogen synthesis’

GLUCOSE

oxidation via oxidation via ‘Pentose phosphate pathway’ ‘Glycolysis’

Ribose 5-phosphate Pyruvate Glycolysiszc

Glycolysis: glykys (Greek); sweet + lysis; splitting

Breakdown of glucose A series of -catalyzed reactions (10 reactions)- glycolytic pathway

Glucose

2ADP + 2Pi

2NAD+

2ATP + 2H2 O

2NADH 2Pyruvate

Final : 2 molecules of 3-carbon compound; pyruvate Glycolysis provides the largest flux of carbon in most cells Glycolysis Embden-Meyerhof-Parnas pathway!

Preparatory Phase

Glucose -3-phosphate (x2) Glucose 2Pi ATP / G3P 2NAD 2ATP 4ADP + + 2Pi 2NAD ADP 2NADH + H Glucose-6-phosphate 1,3-Bisphosphoglycerate (x2) 4ATP 2ADP 2NADH Phosphohexose Phosphoglycerate 2ATP 2Pyruvate Fructose-6-phosphate 3-Phosphoglycerate (x2) Phospho- ATP Phosphoglycerate Net: 2ATP, 2NADH -1 ADP Fructose-1,6-phosphate Triosephosphate isomerase Triosephosphate 2-Phosphoglycerate (x2) Rate-determining Reaction Aldolase • Hexokinase/ H2 O Glyceraldehyde-3-phosphate glucokinase Phosphoenolpyruvate (x2) + • phosphate Pyruvate 2ADP kinase • 2ATP Pyruvate (x2) Glycolysis through a can be regulated in several ways!

1. Availability of • GLUT1 (Kt 1.5 mM) vs GLUT2 (Kt 66 mM) • Insulin-responsive GLUT4

2. Concentration of enzymes responsible for rate-limiting steps Insulin stimulates the transcription of the that encode • Hexokinase • Pyruvate kinase • Phosphofructokinase-1 • PFK-2/FBPase-2

3. of enzymes • Allosteric activator/inhibitor 4. Covalent modification of enzymes • Glycolysis Rate-determining reactions: hexokinase vs glucokinase!

• Every tissue Hexokinase • Km ≈ 0.1 mM • G6P is an allosteric

inhibitor normal plasma Glucokinase [glucose] (Vo/Vmax) • Hepatocyte, β-cell

• Km ≈ 10 mM

Relative enzymatic activity • G6P does not inhibit

glucokinase 0 5 10 15 20 [Glucose] mM Glycolysis Rate-determining reactions: phosphofructokinase-1 (PFK-1)!

ATP ADP, AMP

Fructose-6 Fructose-1,6 + ATP + ADP phosphate PFK-1 bisphosphate

citrate F26P

Allosteric inhibitor: ATP, citrate ATP เปน product ของกระบวนการ glycolysis Citrate เปนสารตงตนใน Krebs cycle

Allosteric activators: ADP, AMP, fructose-2,6-bisphosphate (F26P) ADP, AMP ไดจากปฏกรยา ATP F26P เปลยนมาจาก F6P ซงเปน glycolytic intermediate Glycolysis Formation of fructose-2,6-bisphosphate (F26P)!

Fructose-6-phosphate ATP Pi (glycolytic intermediate)

insulin PFK-2 FBPase-2

ADP Fructose-2,6-bisphosphate H2 O

Insulin กระตน phosphofructokinase-2 Glucagon กระตน fructose bisphosphatase-2 (PFK-2) เปนผลให F26P มปรมาณเพมขน (FBPase-2) เปนผลให F26P มปรมาณลดลง ทให glycolysis ถกกระตน ทให glycolysis ถกยบยง (ผานการทงานของ (ผานการทงานของ PFK-1) PFK-1) Glycolysis Rate-determining reactions: pyruvate kinase!

Covalent modification Allosteric control (liver only) (all glycolytic tissues) glucagon F16BP F16BP ADP ATP

PKA PEP PEP P ADP ATP acetyl-CoA Pyruvate long-chain fatty acids ATP carboxylase Pyruvate Pyruvate Pyruvate Pyruvate kinase (L) PP kinase transamination (inactive) H2 O Pi (L/M)

PKA- A PP- phosphoprotein

During , glycolysis is inhibited in the liver (glucagon signal) but unaffected in the muscle : glucagon (êF26P) Hormone: insulin (éF26P) High index: ATP Low energy index: ADP, AMP acetyl-CoA, citrate, LCFA Intermediate: F16P Intermediate: G6P Glucose + -

2Pyruvate 2ATP, 2NADH Glycolysis Other clinical significance- formation of 2,3BPG in RBC!

Bisphosphoglycerate mutase 1,3-Bisphosphoglycerate (x2) 2ADP Phosphoglycerate 2,3-Bisphosphoglycerate (x2) kinase 2ATP 2Pi 3-Phosphoglycerate (x2) 2,3-Bisphosphoglycerate phosphatase

2,3-bisphophoglycerate (2,3-BPG)

2,3-BPG มผลตอการจบกบ O2 ของ (O2 affinity): มมาก จบนอย ปลอยงาย

[2,3-BPG] in normal RBC ≈ 5 mM

[2,3-BPG] > 5 mM (eg. pyruvate kinase deficiency)- O2 delivery ไปยง peripheral tissue

[2,3-BPG] < 5 mM (eg. hexokinase deficiency)- O2 delivery ไปยง peripheral tissue Glycolysis Other clinical significance- fluoride can inhibit enolase!

O Glyceraldehyde-3-phosphate (x2) P O CH2 CH C Dental carries (ฟนผ) 2Pi OH H G3P 2NAD dehydrogenase + Common pathogen: Streptococcus mutans! 2NADH + H O

1,3-Bisphosphoglycerate (x2) P O CH2 CH C O 2ADP OH P Fluoride ion (F-) 2ATP Magnesium ion (Mg2+) ( ของเอนไซม) O 3-Phosphoglycerate (x2) P O CH CH C 2 Inorganic phosphate (Pi) OH O

O Enolase Ÿ Mg2Ÿ F2 ŸPi- inhibitory complex 2-Phosphoglycerate (x2) HO CH2 CH C O ทใหO 2PG เขาถง ไมได Enolase P H O 2 O

Phosphoenolpyruvate (x2) CH2 C C O Pyruvate 2ADP O kinase P 2ATP O

Pyruvate (x2) CH3 C C O O Metabolic Fate of Pyruvate NADH must be reoxidized!

Glucose

NAD+ NAD+ 2 + 2CO2 2 Lactate NADH NADH Anaerobic condition Anaerobic condition 2 Pyruvate Vigoriously contracting muscle RBC NADH

4CO2 NAD+ 2 Acetyl-CoA

Krebs cycle

4CO2 + 4H2 O

ETC Aerobic condition Anaerobic Glycolysis Lactic and !

Skeletal muscle, RBC O O O O NADH + H+ NAD+ C C C O HO C H lactate CH 3 dehydrogenase (LDH) CH 3 Pyruvate Lactate

Baker yeast

+ CO2 NADH NAD O O O OH CH C C CH C CH C H 3 pyruvate 3 3 O decarboxylase H dehydrogenase H Pyruvate Acetaldehyde Ethanol Anaerobic Glycolysis Energy harvesting efficiency!

Lactic Fermentation Ethanol Fermentation

+ + 2NAD+ 2NADH 2NADH 2NAD+ 2NAD 2NADH 2NADH 2NAD

Glucose 2Pyruvate 2Lactate Glucose 2Pyruvate 2EtOH + 2CO2

2ADP 2ATP 2ADP 2ATP

ΔG’° = -196 kJ/mol of glucose ΔG’° = -235 kJ/mol of glucose

2ATP 2ATP Efficiency = Efficiency = 196 kJ/mol 235 kJ/mol

= 2(30.5 kJ/mol) = 2(30.5 kJ/mol) 196 kJ/mol 235 kJ/mol = 32% = 26% Anaerobic Glycolysis Rapid energy extraction! Anaerobic glycolysis Aerobic glycolysis + OXPHOS

• Ethanol fermentation (2 ATP) 26% • Glucose + 6O2 6CO2 + 6H2O • Lactic fermentation (2 ATP) 32% 34% (ΔG’° = -2,840 kJ/mol, 32 ATP)

Glucose Glucose

NAD+ NAD+ 2 Ethanol + 2CO2 2 Lactate NADH NADH Anaerobic condition Anaerobic condition Yeast 2 Pyruvate Vigoriously contracting muscle 2 Pyruvate RBC NADH Anaerobic glycolysis (2 ATP) 4CO2 NAD+ 2 Acetyl-CoA สามารถเกดไดเรวกวา Krebs cycle aerobic glycolysis + OXPHOS (32 ATP)

ถง 100 เทา 4CO2 + 4H2 O ETC Aerobic condition Anaerobic Glycolysis Fast-twitch vs slow-twitch muscles fiber!

Fast-twitch fiber Slow-twitch fiber (type II) (type I) Rate of contraction Fast Slow

Metabolism Mainly anaerobic OXPHOS dependent glycolysis Fatigability Quickly Relatively more slowly Muscle histology Pale (pinkish) Red ( in cytochromes) Sport type Spinners Marathoners Slow-Twitch Muscle Fiber in PGC-1α Transgenic Mice

Lin, et al., Nature 2002

WT = wild-type mice Tg = PGC-1α transgenic mice PGC-1α is a transcriptional co-activator which promotes mitochondrial biogenesis Acetyl-CoA Formation

• Aerobic condition • Pyruvate is transported into the mitochondrial matrix • Enzyme: complex (PDH complex)

Pyruvate dehydrogenase complex

Multienzyme Complexes • Catalytic core E1: pyruvate dehydrogenase E2: dihydrolipoyl transacetylase E3: dihydrolipoyl dehydrogenase • Regulatory subunits Pyruvate dehydrogenase kinase Pyruvate dehydrogenase phosphatase Acetyl-CoA Formation PDH complex deficiency- Wernicke-Korsakoff syndrome!

CoA-SH O O + NAD TPP NADH O S-CoA C lipoate C FAD + CO O C pyruvate dyhydrogenase 2 complex (E1 + E2 + E3) CH 3 CH 3 Pyruvate Acetyl-CoA

PDH complex deficiency Wernicke-Korsakoff syndrome

• - inborn error of metabolism • deficiency- chronic alcoholism • Pyruvate is converted into • Neurons- OXPHOS dependent • Metabolic , coma, death • Wernicke encephalopathy + • Treatment Korsakoff psychosis § (fat > protein > CHO) § Thiamine (B1), dichloroacetate Acetyl-CoA Formation PDH complex deficiency- Wernicke-Korsakoff syndrome!

Thiamine (TPP) Thiamine deficiency

Chronic alcoholism Malnutrition, malaborption Liver- loss ability to store B1

Brain (neurons)- mainly aerobic glycolysis + OXPHOS Shrinkage of the cerebral cortex and atrophy of basal forebrain regions Wernicke encephalopathy Korsakoff psychosis Confusion Amnesia Loss of muscle coordination Confabulation Vision changes Hallucination Regulation of the PHD complex Product inhibition!

To control ‘carbon flux’ (acetyl unit) [NADH] that enters the Krebs’ cycle FAD + NAD+ [NAD ] SH + SH NADH+H

dihydrolipoyl dehydrogenase (E3) OH S FAD CO2 CH 3 C TPP S S Hydroxyethyl- R TPP Lipoamide S HS pyruvate dihydrolipoyl HS dehydrogenase (E1) transacetylase (E2) O R O O O CH C C 3 TPP CH C S CH C S CoA O 3 3 Acetyl-CoA Pyruvate HS R CoA Acetyl-dihydrolipoamide [acetyl-CoA] [CoA] Regulation of the PHD complex Covalent modification!

P

ADP Pyruvate ADP dehydrogenase complex CoA (inactive) H2 O NAD+ 2+ Pyruvate Ca PDK PDP 2+ Mg ATP Acetyl-CoA Pyruvate dehydrogenase Pi NADH complex (active) ATP

[acetyl-CoA] [NADH] [ATP] Phosphorylation at E1 PDH complex [NAD+] [CoA] [ADP] is inhibited Regulation of the PHD complex Summary!

1) Product inhibition

E2 (dihydrolipoyl transacetylase) is inhibited by [acetyl-CoA] [CoA]

E3 (dihydrolipoyl dehydrogenase) is inhibited by increased [NADH] [NAD+]

2) Covalent modification- phosphorylation of E1

E1- (pyruvate dehydrogenase) is inactive when phosphorylated

PDK- activated by ATP, acetyl-CoA, NADH PDP- activated by Ca2+ and Mg2+ The Krebs Cycle

Glucose Glycolysis 2 Pyruvate PDH complex 2 Acetyl-CoA

6 NADH

2 FADH2 2 GTP (ATP)

Krebs cycle Oxidative Phosphorylation (OXOHOS)

1 NADH 2.5 ATP ETC 1 FADH2 1.5 ATP ATP from Complete Oxidation of Glucose Gluconeogenesis

Gluco; glucose, neo; new, genesis; synthesis

Gluconeogenesis: a metabolic pathway that regenerates glucose form non-carbohydrate carbon substrates

Pyruvate Lactate Glucose

Glycerol Glucogenic Gluconeogenesis

ATP Glucose Pi Glycolysis hexokinase/ glucose-6- Gluconeogenesis glucokinase phosphatase ADP Glucose-6-phosphate H2 O phosphogluco isomerase ATP Fructose-6-phosphate Pi PFK-1 FBPase-1

ADP Fructose-1,6-bisphosphate H2 O aldolase triosephosphate isomerase G3P DHAP 2NAD+ + 2Pi 2NAD+ + 2Pi G3PDH 2NADH 2NADH 1,3-Bisphosphoglycerate (x2) 2ADP 2ADP PGK 2ATP 2ATP 3-Phosphoglycerate (x2) phosphoglycerate mutase 2-Phosphoglycerate (x2) enolase 2GDP 2ADP Phosphoenolpyruvate (x2) PEP carboxykinase 2GTP pyruvate kinase Oxaloacetate (x2) 2ATP Pyruvate (x2) 2ADP 2ATP Gluconeogenesis Hydrolysis of G6P by glucose-6-phosphatase in the ER!

• An active site of glucose-6-phosphatase faces towards the ER lumen • Separation of gluconeogenesis and glycogenolysis from glycolysis • Plays a key role in homeostatic regulation of blood levels Gluconeogenesis - synthesis of glucose from lactate!

Liver Muscle Glucose blood glucose Glucose + ADP+Pi NAD+ NAD ADP+Pi

ATP NADH NADH ATP 2Pyruvate 2Pyruvate NADH lactate lactate NADH dehydrogenase dehydrogenase NAD+ NAD+ 2Lactate blood lactate 2Lactate

Sources of lactate • • Fast-twitch muscle fiber Gluconeogenesis Synthesis of glucose from !

Fat mobilization • Shortage of liver glycogen (long ) • o Primarily expressed in liver • Dihydroxyacetone phosphate (DHAP) is used to synthesize glucose in order to maintain blood glucose levels Gluconeogenesis Synthesis of glucose from glucogenic amino acids!

Protein mobilization • Most dietary amino acid Gluconeogenesis • Structural protein (muscle Oxaloacetate protein) is the last source of

The material for gluconeogenesis Krebs (after glycogen and fat) Cycle • Glucogenic amino acids

Gluconeogenesis Glucose-alanine cycle!

+ Ammonia (NH4 ) • Toxic product from protein degradation • Glutamate transfers ammonia to pyruvate Alanine • Transport ammonia from muscle to the liver Glycolysis vs Gluconeogenesis - uneconomical process!

Glycolysis Gluconeogenesis

Glucose Glucose 4ADP + 2GDP 2ADP + 2Pi 6Pi + 2NAD 2NAD+ 4ATP + 2GTP 2ATP + 2H2 O 6H2 O 2NADH 2NADH 2Pyruvate 2Pyruvate

Net reaction:2ATP + 2GTP + 4H2O 2ADP + 2GDP + 2Pi Coordinated Regulation of Glycolysis & Gluconeogenesis Coordinated Regulation of Glycolysis & Gluconeogenesis expression control- hexokinase/glucose-6-phosphatase!

Increased of the enzymes in the pathways

• High energy demand • A need to increase production of o low [ATP] glucose o high [AMP] o low blood [glucose] o vigorous muscle contraction o glucagon signaling • Greater glucose consumption o high blood [glucose] o insulin signaling

Hexokinase Glucose-6-phosphatase Coordinated Regulation of Glycolysis & Gluconeogenesis Allosteric control- PFK-1/FBPase-1!

Gluconeogenesis

ATP Fructose-6-phosphate Pi ATP ADP PFK-1 AMP FBPase-1 citrate F26F ADP Fructose-1,6-bisphosphate H2 O

Glycolysis High energy utilization Low energy utilization • ATP hydrolysis: [ADP] and [AMP] • ATP hydrolysis: [ATP] • OXPHOS slows down: [citrate] ATP Fructose-6-phosphate Pi (glycolytic intermediate) insulin PFK-2 FBPase-2 glucagon

ADP Fructose-2,6-bisphosphate H2 O Coordinated Regulation of Glycolysis & Gluconeogenesis Mixed mechanism- pyruvate kinase/pyruvate carboxylase!

Covalent modification Allosteric control (liver only) (all glycolytic tissues) glucagon F16BP F16BP ADP ATP

PKA PEP PEP P ADP ATP acetyl-CoA Pyruvate long-chain fatty acids ATP carboxylase Pyruvate Pyruvate Pyruvate Pyruvate kinase (L) PP kinase transamination (inactive) H2 O Pi (L/M) Alanine Coordinated Regulation of Glycolysis & Gluconeogenesis Acetyl-CoA- antagonistic effect on glucose metabolism!

Glucose

Gluconeogenesis

Oxaloacetate pyruvate carboxylase Glycolysis Pyruvate pyruvate kinase Glucose pyruvate DH complex Acetyl-CoA

Kerbs cycle

Energy Coordinated Regulation of Glycolysis & Gluconeogenesis Summary!

Hexokinase/glucose-6-phosphatase • Alteration in gene expression • Insulin, glucagon and other signals that reflect cellular energy requirement

PFK-1/FBPase-1 • Alloteric control • ATP, ADP, AMP, citrate, F26P • Insulin and glucagon influence the formation of F26P

Pyruvate kinase/pyruvate carboxylase • Allosteric control and covalent modification • Acetyl-CoA Glycogen

Structure of Glycogen

• Polymers of glucose • α(1 4) glycosidic (linked) and α(1 6) glycosidic bonds (branched) • Cytosolic granules (β-particle)

Function of Glycogen

• Endogenous major storage reserve of glucose o Muscle glycogen (1-2% of FW) ² Important fuel during prolonged strenuous (4-6 hr) o Liver glycogen (10% of FW) ² Regulate plasma glucose (8-10 hr) • Regulate osmotic pressure inside the cell o 10% of FW of the liver: 40,000x reduce in osmotic pressure

Glycogen Synthesis A starting point of a glycogen chain- !

CH2 OH Glycogenin O H H H Glycogenin OH + OH H HO O UDP Tyr194 H OH glucosyl UDP-glucose (intrinsic activity of glycogenin) UDP

CH2 OH O H H Glycogenin + H OH H Tyr194 HO O UDP H OH glucosyl Liver, muscle transferase (x7 more times) UDP-glucose (chain extending) UDP

Glycogenin

Tyr194 Glycogen primer Glycogen Synthesis Elongation- **!

CH2 OH CH2 OH CH2 OH H O H H O H H O H H 4 H 1 4 H 1 4 OH H 1 OH H OH H HO O UDP + HO O O H OH H OH H OH UDP-glucose Nonreducing end of a glycogen chain (glucose residue > 4) UDP glycogen synthase

CH2 OH CH2 OH CH2 OH New H O H H O H H O H nonreducing 4 H 1 4 H 1 4 H 1 OH H OH H OH H end HO O O O H OH H OH H OH Elongated glycogen

activated by G6P, insulin (after meal) Glycogen synthase inhibited by glucagon, (during meal, sympathetic) Glycogen Synthesis Branching- glycogen-branching enzyme!

Glycogen core glycogen-branching enzyme point Glycogen core

• branching- a glycogen chain has at least 11 glucose residues • transfer of 6-7 glucose residues from the nonreducing end to an interior position

Glycogen Synthesis Summary!

• Start ü Glycogenin ü Glucosyl transferase (intrinsic activity of glycogenin) ü Glycogenin + 8 glucose residues = glycogen primer • Elongation ü Nonreducing end + UDP-glucose ü Glycogen synthase***

• Branching ü Transfer of a terminal fragment of 6-7 glucose residues from nonreducing end ü Forming α(1 6) ü Glycogen-branching enzyme Glycogenolysis Step 1- glycogen **!

Nonreducing ends

Glycogen

P P P

P P P

activated by glucagon, epinephrine, Ca2+ Glycogen phosphorylase inhibited by insulin, glucose Glycogenolysis Step 2- glycogen debranching enzyme!

glycogen debranching enzyme Glucose

Unbranched glycogen (

Oligo α(1 6) to α(1 4) glucan-transferase α(1 6) glucosidase Glycogenolysis Step 3- , glucose-6-phosphatase (liver only)!

O O O P P P

O O O P P P Glucose-1-phosphate phophoglucomutase

P P P O O O

P P P O O O

Glucose-6-phosphate

Muscle glucose-6-phosphatase Liver

Free glucose Pi GLUT2 Glycolysis Plasma glucose Glycogenolysis Summary!

• Glycogen phosphorylase*** ü Removes the terminal glucose residue of a glycogen chain as G1P ü Rate-limiting step of glycogenolysis

• Glycogen debranching enzyme ü Oligo α(1 6) to α(1 4) glucan-transferase ü α(1 6) glucosidase, resulting in a free glucose

• Phosphoglucomutase/ glucose-6-phosphatase (liver only) ü Muscle: G1P G6P glycolysis ü Liver: G1P G6P free glucose blood Control of Glycogen Metabolism Allosteric control!

Glycogen Glycogen Glycogen phosphorylase b synthase a (inactive) (active) synthesis

ATP AMP G6P Glucose

Glycogen Glycogen Glycogenolysis phosphorylase a synthase b (active) (inactive)

Glycogen phosphorylase (liver): Glycogen synthase: ‘glucose sensor’ ‘G6P sensor’ Control of Glycogen Metabolism Hormonal control- glycogen phosphorylase!

Glycogen phosphorylase b glucagon (inactive) (liver)

2Pi 2ATP phosphorylase a phosphorylase b phosphatase kinase 2H2 O 2ADP

epinephrine, Ca2+ Glycogen (muscle) P phosphorylase a P (active) Control of Glycogen Metabolism Hormonal control: glycogen synthase!

Insulin

3ADP 3ATP GSK3

P Glycogen Glycogen P synthase b synthase a (inactive) (active) P phosphorylase a phosphatase 3Pi

Insulin Glucogan (liver) Ephinephrine (muscle) Control of Glycogen Metabolism Summary!

To increase plasma glucose To decrease plasma glucose ✓ Glycogenolysis ✗ Glycogenolysis ✗ Glycogen synthesis ✓ Glycogen synthesis + Glycogen phosphorylase: + Glycogen synthase glucagon, epinephrine insulin AMP, Ca2+ G6P - Glycogen synthase - Glycogen phosphorylase glucagon, epinephrine insulin, glucagon glucose, ATP : high plasma [glucose] • Fasting hyperglycemia (at least 8 hours after meal) plasma [glucose] > 130 mg/dl • Postprandial hyperglycemia (2 hours after meals) plasma [glucose] > 180 mg/dl

อาการของ hyperglycemia • Temporary hyperglycemia- asymptomatic

• Chronic hyperglycemia- diabetes mellitus Polyphagia, polydipsia, polyuria Macrovascular and microvascular complications  NORMAL plasma [glucose] = 80 - 110 mg/dL  : low plasma [glucose]

Plasma [glucose] < 60 mg/dl หรอตจนมอาการ ..Metabolic emergency..

อาการของ hypoglycemia

Adrenergic manifestation: palpitating, sweating, tachycardia

Glucagon manifestation: hunger, nausea, vomiting, headache

Neuroglycopenia: impaired judgment, confusion, seizure, coma

 NORMAL plasma [glucose] = 80 - 110 mg/dL  Plasma [glucose] mg/dL

350 Glycolysis Gluconeogenesis 300 Glycogen synthesis Glycogenolysis 250

200

150

100 Normal

50

0 0 1 2 3 4 5 6 Hours Plasma [glucose] mg/dL

350

300

250 DM 200

150

100 Normal

50

0 0 1 2 3 4 5 6 Hours Diabetes mellitus A defining characteristic of DM is chronic hyperglycemia!

Plasma [glucose] mg/dL Cause Inability to lower blood 350 glucose 300

250 DM Classic symptoms Polydipsia, polyphagia, 200 polyuria 150

100 Normal

50

0 0 1 2 3 4 5 6 Hours Diabetes mellitus World major metabolic disease!

WHO- 346 million people worldwide (August 2011) Diabetes mellitus Type 1 DM!

β-cells are destroyed Diabetes mellitus Type 2 DM!

Genetic factor

• มความผดปกตของ gene ทใหการ ตอบสนองของเซลลตอ insulin ลดลง Environment • Sedentary lifestyle (ไมออกกลงกาย) Genetic + Environment • Too much fat/sugar intake Diabetes mellitus Main symptoms! Pentose Phosphate Pathway Overview!

Nonoxidative Oxidative phase phase

Glucose-6-phosphate + NADP 2GSH glutathione reductase NADPH GSSG 6-Phosphogluconate Fatty acids, + sterols, etc. , NADP reductive CO2 NADPH Ribulose-5-phosphate Precussors

Ribose-5-phosphate

Nucleotides, coenzymes, DNA, RNA Pentose Phosphate Pathway Role of PPP!

Ribose-5-phosphate and NADPH synthesis Rapidly dividing cells: bone marrow, skin, intestinal mucosa

NADPH Reductive biosynthesis: fatty acids, , Fat tissue, liver, lactating mammary glands, , testis/ovaries Potent : recycle GSH Pentose Phosphate Pathway Control of PPP: G6P is partitioned between glycolysis and PPP!

Glucose

Glycolysis Glucose-6-phosphate + NADP 2GSH G6PD glutathione reductase NADPH GSSG 6-Phosphogluconate Fatty acids, + sterols, etc. NADP reductive biosynthesis CO2 NADPH Ribulose-5-phosphate Precussors

Ribose-5-phosphate

NADP+ is an allosteric activator of G6PD Pentose Phosphate Pathway G6PD deficiency- epidemiology!

• Most common enzyme defect • Affected > 400 million people worldwide (2008) • Distribution of G6PD deficiency resembles that of malaria

Glucose-6-phosphate NADP+ glucose-6-phosphate dehydrogenase NADPH 6-phosphoglucono lactonase 6-Phosphogluconate

phosphogluconate NADP+ dehydrogenase M a l a r i a l B a n d

CO2 NADPH

Ribulose-5-phosphate phosphopentose isomerase Ribose-5-phosphate Pentose Phosphate Pathway G6PD deficiency: genetic defects!

X-linked recessive Most are missense mutations Pentose Phosphate Pathway G6PD deficiency: clinical manifestation!

• Most G6PD-deficient individuals are asymptomatic • Severe infection, some drugs, fava beans induce acute hemolysis

Jaundice Dark urine • Deposition of bilirubin • Hemoglobinuria Pentose Phosphate Pathway G6PD deficiency: molecular mechanism of acute hemolysis!

Molecular O2 Oxidative fava beans e infection some drugs . Superoxide anion O2

2H+ e Induce oxidative damage to hemoglobin and RBC membrane GPx or catalase Hydrogen peroxide H2 O2 H2 O ( peroxidation), + resulting in HEMOLYSIS 2H e 2GSH GSSG H O 2 . Hydroxyl radical OH GR NADP+ NADPH

Glucose 6-phospho- 6-phosphate G6PD Metabolism of Hexoses other than Glucose Fructose metabolism!

fructokinase Liver Fructose Fructose-1- Muscle phosphate ATP ATP ADP fructose-1- hexokinase phosphate ADP aldolase NADH NAD+ ATP Fructose-6- Glyceraldehyde alcohol DH Glycerol phosphate ADP glyceraldehyde kinase ATP + glycerol GAP kinase triosephosphate glycerol ADP isomerase phosphate DH GLYCOLYSIS DHAP GAP

NAD+ NADH Metabolism of Hexoses other than Glucose Defect in fructose metabolism: deficiency!

fructokinase Liver Fructose Fructose-1- phosphate ATP ADP () Rare genetic disorder, mutations in KHK gene Mode of inheritance: autosomal recessive Defect: liver cannot convert fructose to F1P Finding: fructosuria Sign and symptom: benign, mostly, asymptomatic Metabolism of Hexoses other than Glucose Defect in fructose metabolism: hereditary fructose intolerance!

fructokinase Liver Fructose Fructose-1- phosphate ATP ADP fructose-1- phosphate aldolase

Glyceraldehyde + DHAP Hereditary fructose intolerance Severe form of defect in fructose metabolism, ALDOB gene Mode of inheritance: autosomal recessive Defect: liver cannot metabolize F1P Finding: accumulation of F1P, liver damage Treatment: avoid fructose and sucrose Metabolism of Hexoses other than Glucose Galactose metabolism!

CH OH CH OH CH OH 2 ATP ADP 2 2 HO O H HO O H H O H H H H O O OH H OH H 2- OH H H OH H OPO3 HO O P O P O H OH H OH H OH O O Galactose Galactose-1-phosphate UDP-Glucose

Galactose-1-phosphate UDP-galactose- uridylyl transferase 4-epimerase

CH2 OH CH2 OH H O H HO O H H H O O OH H 2- OH H HO OPO3 H O P O P O Uridine H OH H OH O O Glucose-1-phosphate UDP-Galactose Metabolism of Hexoses other than Glucose Defect in galactose metabolism: !

CH OH CH OH CH OH 2 ATP ADP 2 2 HO O H HO O H H O H H H H O O OH H Galactokinase OH H 2- OH H H OH H OPO3 HO O P O P O Uridine H OH H OH H OH O O Galactose Galactose-1-phosphate UDP-Glucose

Galactose-1-phosphate UDP-galactose- uridylyl transferase 4-epimerase

CH2 OH CH2 OH H O H HO O H H H O O OH H 2- OH H HO OPO3 H O P O P O Uridine H OH H OH O O Glucose-1-phosphate UDP-Galactose

Galactosemia • most cases are caused by defect in galactose-1-phosphate uridylyl transferase deficiency (genetics) • failure to thrive, mental retardation, death from liver damage Metabolism of Hexoses other than Glucose !

CH OH CH OH 2 ATP ADP 2 HO O H HO O H H H OH H Galactokinase OH H 2- H OH H OPO3 H OH H OH Galactose Galactose-1-phosphate

Galactosemia • galactose-1-phosphate is an allosteric inhibitor of galactokinase • galactose can be reduced to galactitol • accumulation of galactitol in the lens of the eye causes cataract (ตอกระจก)

CH2 OH H C OH HO C H HO C H H C OH

CH2 OH Galactitol Metabolism of Alcohol

Consequences of Excessive Alcohol Consumption • alcohol induced hypoglycemia • fatty liver • liver cirrhosis