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Chem331 Glycolysis Gluconeo

Chem331 Glycolysis Gluconeo

4/20/21

Glycolysis

Glycolytic endpoints - depending on which and conditions, results in the production of , lactate and CO2, H2O via pyruvate – This is the predominate fate of glucose in mammalian cells

– Limited potential energy w/o O2 . Captured as ATP – Pathway is found in all cells of the body – This is primarily a cytosolic pathway

Net reaction: + Glucose + 2 ADP +2 Pi + 2 NAD <-> 2 Pyruvate + 2 ATP + 2 NADH

The Fates of Pyruvate From Fate of Puruvate Glycolysis Pyruvate in metabolism. Glucose and other monosaccharides are catabolized through glycolysis into pyruvate.

Pyruvate can be decarboxylated and enter the cycle, producing other metabolic Pyruvate produced in glycolysis can be used by cells in several ways. In intermediates or contributing to animals, pyruvate is normally converted to acetyl-, which is then oxidized in the TCA cycle to produce CO2. When is limited, pyruvate ATP production. can be converted to lactate. Alcoholic in converts

pyruvate to ethanol and CO2.

Glycolysis

The overall metabolism can be considered to be in two stages. In the first stage there is a cost of energy (in the form of ATP). Glucose is metabolized to two trisoses - 3 phosphoglycerate.

In essence the is activated and prepared for energy production by . The second stage results in the partial oxidation to pyruvate and the formation of energy currency (NADH and ATP).

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-2 HO CH2 O3PO CH2 -2 O3PO CH2 O CH2OH H O H ATP ADP H O H

OH H OH H H OH H OH Reactions and Thermodynamics of Glycolysis OH OH OH OH Phosphoglucose OH OH H H H OH -6- Glucose Glucose-6-phosphate ATP Phosphofructo- ADP

-2O PO -2 3 CH2 O CH2 OPO3

-2 Glyceraldehyde 3-Phosphate

O OPO3 O H Aldolase OH C C H H OH HC OH HC OH OH H -2 + -2 CH2 OPO3 NADH NAD Pi CH2 OPO3 Fructose-1,6-bisphosphate 1,3-Bisphosphoglycerate Glyceraldehyde 3-Phosphate -2 ADP CH2 OPO3 Phosphoglycerate Triose Phosphate kinase Isomerase C O

ATP H2C OH - O O Dihydroxyacetone C

HC OH

-2 CH2 OPO3 3-Phosphoglycerate GLYCOLYSIS Phosphoglycerate O O- C - HC OPO -2 O O 3 C CH OH 2 HC OH 2-Phosphoglycerate + CH3 NAD Lactate

H2O NADH ATP ADP - O O- O O- O O OAA, Lactate, C C C Ethanol, or -2 Acetyl CoA C OPO3 C OH C O Pyruvate Spontaneous Krebs Cycle, Kinase CH2 CH2 CH3 Phosphoenolpyruvate Pyruvate () Pyruvate (keto) Metabolism

Steady-State Concentrations of There are a few items you need to keep in mind Glycolytic Intermediates when looking at metabolism.

• The structure of the reactants and products These steady-state • Where did the carbons come from. Be able to trace the concentrations are used to obtain the cellular values of ΔG carbons from glucose through each step of glycolysis • What are the important points for each … regulation, reaction mechanism, … • The overall control of glycolysis and the fate of the metabolism – This is more than just memorizing the pathway but you do need to know that too.

Reactions of Glycolysis Metabolism Nomenclature points - / Hexokinase - (GK/HK)

bis vs. di - two phosphoryl groups bonded by a phosphodiester bond is a "di" phosphate (ADP). While a "bis" phosphate means that two phosphates are bonded onto the molecule on different sites.

Enolates - "ene" is descriptive for a double bond the "ol" refers to an group. If there is a phosphate on the Key glycolytic enzyme OH of an enolate then it is a enol phosphate. This is -1st step in glycolysis; DG large, negative -Hexokinase (and glucokinase) act to phosphorylate glucose and keep different than an acyl phosphate. Both enol phosphates “trap” Glucose in the cell and acyl phosphates are high energy bonds. -1 ATP is consumed - is considered an irreversable step. Also a key glycolytic step GK is NOT inhibited by G6P

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Reactions of Glycolysis Metabolism Hexokinase Glucokinase / Hexokinase - (GK/HK)

The specific transfer of a -Glucokinase in , pancreasFasting Glc b cells, and phosphoryl from ATP to glucose (maintenance of glucose levels and glucose responsive tissues) instead of water is possible due to Vmax GK the in -Hexokinase in nearly all tissues - non specific for various

HK/GK once ATP and glucose is Activity HK Km for glucose is 0.1 mM; GK Km for glucose is 10 mM. bound. (this is an example of Enz induced fit) Blood Glc: normal 4 - 5.5, /sleeping 3.5Vmax mMHK, post meal 6.5-10 mM Intracellular glucose ranges from 0.2 – 2 mM depending on cell and state The (a) open and (b) closed states of 0 5 10 15 20 mM Glc Therefore - HK has a High affinity for glucose while GK has a Low affinity. yeast hexokinase. Binding of glucose HK Km GK Km (green) induces a conformation change that closes the , as predicted - The function of GK is to remove glucose from the blood following a meal by Daniel Koshland. HK – but not GK is regulated. HK – is allosterically inhibited.

Phosphoglucose Isomerase (PGI) Phosphoglucoisomerase

-Isomerase reaction Glucose-6-P to Fructose-6-P -Phosphohexose isomerase = phosphoglucose isomerase Why does this reaction occur? -The reaction is a controlled sequence of ->open structure / reaction / close ring – next step (phosphorylation at -Acid/ base catalyst mechanism C-1) would be tough for -Fructose 6-P produced - no energy input hemiacetal -OH, but easy for primary -OH – isomerization activates C-3 for cleavage in aldolase reaction Phosphoglucoisomeras Ene-diol intermediate in this with fructose-6-P (blue) reaction bound.

A mechanism for (PFK) phosphoglucoisomerase key glycolytic enzyme

-ATP consumed, another phosphoryl transfer (kinase) reaction -Fructose 1-6- bis phosphate produced

-Rate determining reaction - first commited step in glycolysis -Commited step with large –DG -Highly regulated The phosphoglucoisomerase mechanism involves opening of the pyranose ring (step 1), proton abstraction leading to enediol formation (step 2), and proton addition to the double bond, followed by ring closure (step 3)

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Phosphofructokinase – a Second Phosphorylation Driven by ATP Phosphofructokinase

-Allosterically regulated. - Homotetramer in mammalian cells. - Two conformations: Active (R) and Inactive (T) - TWO ATP Binding sites – active site and regulatory site - PFK is inhibited by high energy signals, ATP and Citrate. A feedforward and mechansim. - Activated by low energy signal AMP – which also competitively binds at the regulatory . Phosphofructokinase is the second priming reaction of - AMP reverses ATP inhibition (thus an ) glycolysis. ATP is consumed in this priming reaction, so that - Fructose-2,6-bisphosphate is strong allosteric activator more ATP can be produced further along the pathway. Impact of : • PFK increases activity when energy status is low • PFK decreases activity when energy status is high

F-2,6-BP regulates Phosphofructokinase behaves cooperatively Phosphofructokinase at high [ATP]

Phosphofructokinase is regulated by fructose-2,6- bisphosphate, a potent allosteric activator that increases the At high ATP, phosphofructokinase (PFK) behaves affinity of phosphofructokinase for the fructose-6-P. cooperatively and the activity plot is sigmoid.

Phosphofructokinase is activated by F- F-2,6-BP regulates 2,6-BP Phosphofructokinase Fructose-2,6- bisphosphate activates phosphofructokinase, increasing the affinity of the enzyme for fructose-6-phosphate and restoring the hyperbolic dependence of enzyme activity on substrate Phosphofructokinase is regulated by fructose-2,6- concentration. bisphosphate, a potent allosteric activator that increases the affinity of phosphofructokinase for the substrate fructose-6-P.

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F-2,6-BP reverses the inhibition of PFK by Regulation of PFK-2 ATP

Rate-limiting step Kinase A – Ser/Thr kinase. cAMP activates PKA F-2,6-BP stimulates cAMP production and degradation is PFK by decreasing regulated by hormone action • and epinephrine the inhibitory effects of increase cAMP ATP. • leads to decrease in [cAMP]

AMP is an allosteric activator of PFK leads to F26bP by activates AMP Kinase (AMPK) further activating PFK

Regulation of phosphofructokinase-2 (PFK-2). PFK-2 has both kinase and activities. The activity of PFK-2 is regulated by PKA and AMPK.

Aldolase Triose Phosphoisomerase (TPI)

Intraconversion of GAP and DHAP Molecule split in equal - Allows for production of 2 molecules of glyceraldehyde 3-P carbons -glyceraldehyde - - Rate of the reaction is limited to diffusion. The protein is catalytically 3-P (GAP) and perfect dihydroxyacetone P - TPI activityallows the products of the first stae of glycolysis to (DHAP) proceed through the second stage as glyceraldehyde 3-phosphate

-Retro aldol reaction involving a Shiff Base – catalytic mechanism -Enolate intermediate -Note where the carbons come from.

The structure of triose phosphate isomerase TPI Mechanism • Triose phosphate isomerase with substrate analog • 2-phosphoglycerate shown in cyan. • This reaction makes it possible for both products of the aldolase reaction to continue in glycolysis • The reaction involves an ene-diol mechanism • Glu165 in the active site A reaction mechanism for triose phosphate isomerase. In the acts as a general base yeast enzyme, the catalytic residue is Glu165.

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Glyceraldehyde 3-Phosphate Common Molecules in Dehydrogenase (GAPDH) Chemistry - Leads to the first production of energy equivilants -Withdraws 2 electrons / NAD+ is acceptor (reduction reaction) -NADH leads to later production of ATP via ox phos -BPG is an acyl phosphate and is therefore BPG is "high energy" mixed anhydride - -> use NADH/NAD+ or NADPH/NADP

Numerous molecules participate in redox chemistry in . NAD+ is a small redox active organic molecule that is a critical in many enzymatic reactions. Electrons transferred to NAD+ are used in subsequent reactions, such as the .

Phosphoglycerate Kinase (PGK) (PGM)

• A kinase but different from the Isomerase or mutase reaction protein discussed earlier (how so?) -Phosphate is transferred from 3 PG to the enzyme at a histadine residue • ATP produced through -The thermodynamics are essentually even so it is easily reversable substrate level -This reaction is nessesary for the phosphorylation (O2 is not formation of enolase another high energy involved such as in oxidative intermediate phosphorylation) • The phosphoryl group of C1 of 1,3 BPG is transferred to the beta phosphoryl of ADP • The active site is closed off from water once the substrate binds similar to the mechanism found with hexokinase • The formation of 1,3 BPG has a positive standard state free energy change. The reaction can proceed due to thermodynamic coupling with the PGK reacton

PGM – Rxn Mechanism Enolase

Dehydration of water - Formation of an enol group - high energy product – PEP -The overall DG for the reaction is -1.8 kJ/mol

This is an exchange of phosphate from C2 to C3 via covalent catalyst/acid base mechanism involving phosphotransfer to Histadine

Histadines are often involved in phosphate transfer this is not a kinase and is different from the phosphorylation observed with threonine and

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Pyruvate Kinase (PK) (PK) key glycolytic enzyme • These two ATP (from one glucose) can be viewed as the "payoff" of glycolysis • Large, negative DG – indicating that this reaction is subject to regulation -Substrate level phosphorylation / ATP produced by the release of free • PK is allosterically activated by AMP, F-1,6-bisP energy from PEP • PK is allosterically inhibited by ATP and acetyl-CoA - Committed irreversible step • Understand the keto-enol equilibrium of pyruvate; it is the key to understanding -Transfer of phosphoryl to ADP produced second ATP the pyruvate kinase reaction -Spontaneous shift (tautomerize) from enol to keto form yielding pyruvate -Dehydration of 3PG would not produce a high energy enol phosphate.

Active as a tetramer Pyruvate Kinase Regulation

Two different isozymes: L (liver) and M (muscle) Both are tetramers. §PK is allosterically activated by the substrate PEP §Feed forward activation by F 16 BP §ATP and inhibits §Only the Liver form is phosphorylated at C terminal by PKA (remember cAMP) The structure of the pyruvate kinase tetramer is sensitive to §The resulting phosphorylation shifts the enzyme from tetrameter (active) bound ligands. Shown are the inactive E. coli enzyme in the to monomer (inactive) form absence of ligands (left), and the active form of the yeast dimer - This type of regulation is only observed in liver - why only in the liver (right), with fructose-1,6-bisphosphate (an allosteric regulator, and why is that important? Think in terms of energy needs during fight or flight. Muscle want ATP and liver can use other forms of + blue), substrate analog (red), and K (gold). energy sparing glucose for other tissues.

-2 HO CH2 O3PO CH2 -2 O3PO CH2 O CH2OH H O H ATP ADP H O H

OH H OH H H OH H OH OH OH OH OH Phosphoglucose OH Hexokinase OH H H H OH Isomerase Fructose-6-phosphate Pyruvate Kinase Regulation Glucose Glucose-6-phosphate ATP Phosphofructo- kinase ADP

-2 Liver PK – Liver uses glc for storage and makes glucose in O3PO CH2 O CH OPO -2 2 3

-2 Glyceraldehyde 3-Phosphate

O OPO3 O H Dehydrogenase Aldolase OH C C H H OH times of need. HC OH HC OH OH H -2 + -2 CH2 OPO3 NADH NAD Pi CH2 OPO3 Fructose-1,6-bisphosphate • Inhibited after PKA phosphoryltation 1,3-Bisphosphoglycerate Glyceraldehyde 3-Phosphate -2 ADP CH2 OPO3 • F-1,6 bP allosteric activator (feed forward – high glc signal) Phosphoglycerate Triose Phosphate kinase Isomerase C O

ATP H2C OH - • Inhibited by ATP, Ala and Acetyl-CoA (all high E signals) O O Dihydroxyacetone C

HC OH

-2 CH2 OPO3 Muscle PK – Uses Glc for ATP production. 3-Phosphoglycerate GLYCOLYSIS Phosphoglycerate • Only stimulated by F-1,6 bP Mutase O O- • Not phosphorylated C - HC OPO -2 O O 3 C CH OH • Focus on creating ATP 2 HC OH 2-Phosphoglycerate + CH3 Enolase NAD Allows liver to stop using and instead Lactate H2O produce Glc while muscles and other NADH ATP ADP - O O- O O- O O OAA, Lactate, C C C tissues continue to use Glc (from liver and Ethanol, or -2 Acetyl CoA C OPO3 C OH C O Pyruvate Spontaneous Krebs Cycle, ) in low E or high stress states Kinase CH2 CH2 CH3 Fatty Acid Phosphoenolpyruvate Pyruvate (enol) Pyruvate (keto) Metabolism

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How Do Cells Regulate Energy of glycolysis Glycolysis?

The elegant evidence of regulation - which reactions are exothermic and endothermic how does this relate to regulation Standard state DG values are scattered, with both plus and minus values and no apparent pattern - total amount of ATP produced by metabolism of ·The plot of DG values in cells is revealing: glucose to pyruvate - net gain of 2 ATP (fate of – Most values near zero NADH depends on cell type and oxidation state – 3 of 10 reactions have large, negative DG of the cell) These 3 reactions with large negative DG are sites - maximum value of 3 ATP can be formed from of regulation (HK, PFK, PK) NADH Regulation of these three reactions can turn glycolysis off and on

Intermediate kJ/mol Phosphoenolpyruvate −61.9 Energetics of Glycolysis 1,3–bisphosphoglycerate to 3- −49.3 phosphoglycerate + Pi Phosphocreatine −43.0

ATP to AMP and PPi −45.6

ADP to AMP and Pi −32.8 Acetyl-CoA −31.4

ATP to ADP and Pi −30.5 Glucose-3-phosphate −20.9

PPi to 2 Pi −19.2 Fructose-6-phosphate −15.9

AMP to adenosine and Pi −14.2 Glucose-6-phosphate −13.8 -3-phosphate −9.2 Energetics of glycolysis. A. In the standard state six of the steps of glycolysis are energetically unfavorable and would proceed in the reverse direction. B. Due to Standard Free Energies of of Some Molecules with a High Phosphate the concentrations of metabolites found in the cell, these reactions proceed Transfer Potential (Strongly Negative ΔG° of Hydrolysis) favorably with much lower DG values.

3 key regulatory Access to the blood -DG steps

Glucose Transporters – (GLUT) Influx of glucose into cells 1) Hexokinase and Glucokinase (HK/GK) – 5 different transporters – 12 transmembrane regions Glucose + ATP -> Glucose -6 phosphate + ADP Glut 1 and Glut 3 Plays a large part in blood glucose stabilization - Present in all cells Hexokinase is inhibited by formation of product - Low Km, high affinity but have a lower general rate of transport Glucokinase is not (more sensitive to glucose concentration). Liver - Low Km results in a HIGH basal level of entry into cells contains GK activity - liver is not subjected to inhibition ® liver gets Glut 2 Liver and pancreatic cells (insulin release) some glucose even if rate of glycolysis is high - Low affinity, high Km Km of glucose of HK << GK -> tissues like brain and muscle get first - Sensitive to blood glucose levels - HOW? - BOTH tissues! - Sensitivity results in the sparing of glucose by liver for brain and shot at glucose muscles (non gluconeogenic) Glut 4 Muscles and Fat - Transport regulated by insulin - Number of receptors on the cell membrane is altered by endocytosis into intracellular stores - Main transporter of glucose for these cells

8 4/20/21

Diabetes and Blood Glucose The Warburg Effect and Cancer

Type I (Insulin Dependent) • Otto Warburg observed in 1924 that rapidly B islets low, non-functioning Due to autoimmune disorder proliferating cancer cells metabolize glucose Typically starts when young mainly to lactate, even when O2 is plentiful

Type II Diabetes (Non Insulin Dependent) • It has been suggested that this behavior arises Low or post-receptor signaling events because cells need more than ATP – they must Poor regulation of Glut Transporter 4 in muscle synthesize large amounts of , amino Increased by obesity May need to supplement endogenous insulin by injection acids, and lipids • This requires lots of NADPH for as Insulin release by pancrease results in a decrease in Blood Glucose levels. -where does the bld glc go? well as intermediates for building blocks -What happens when bld glc levels are too high (short term and long term)? • Cancer cells divert large amounts of glucose to -What happens with too much insulin or insulin w/o high blood glc? the pentose phosphate pathway to produce NADPH

The Warburg Effect and Cancer Cancer and Glycolysis

• Tumors show high rates of metabolism Signaling and • Increased glucose uptake and glycolysis is to be to meet the need of increased cancer pathways regulate the • Resulting O2 use due to glycolysis results in hypoxic condition glycolytic pathway. in small nascent tumors. Cancer cells route up to • expression of HK, PFK, Aldolase, GAPDH, PK, Enolase, 90% of acquired glucose PLK and LDH are all increased in induced cancer cells and into • Hypoxia also increased vasuclar endothelial growth factor (VEGF) - stimulated . lactate and alanine, • is produced and cells transport intracellular H+ to producing large amounts extracellular space. of NADPH • Increased extracellular acidity activates required for the activation of proteases (matrix ) which degrade protein glue (extracellular matrix) around cells. This allows blood vessels to move into tumors and tumors to escape.

Entry Points for Glycolysis

Other monosaccharides catabolized through glycolysis. , fructose, and galactose are also catabolized through glycolysis.

9 4/20/21

Gluconeogenesis - Generation of glucose from pyruvate The principle noncarbohydrate precursors of glucose are lactate, pyruvate, and amino acids. Lactate and amino acids can be converted to glucose by this pathway (glucogenic) - NOT Fatty acids Reactions of gluconeogenesis. • Gluconeogenesis differs from glycolysis by Most amino acids (except leucine and ) are converted into four different reactions (three steps). oxalacetate and then metabolized to glucose. • Pyruvate is converted to oxaloacetate by . This is only in part a reversal of glycolysis. • Phosphoenolpyruvate is formed from oxaloacetate by phosphoenolpyruvate Remember the irreversible reactions of carboxykinase (PEPCK). glycolysis. • The steps of glycolysis now proceed in the reverse direction until fructose-1,6- • Liver and are only real gluconeogenic tissues bisphosphate is synthesized. • This is how liver can provide most of glucose during fasting state - i.e. after the glycogen is gone. • Removal of the last two phosphates to yield glucose is accomplished by fructose bisphosphatase and glucose-6-phosphatase.

Pi Glucose ATP Glucose 6- HK phosphatase Glucose 6- Gluconeogenesis H2O phosphate ADP Glycogen Pi Fructose 6-P ATP Fructose 1,6- PFK Bisphosphatase Fructose H2O 1,6 Bis P ADP

Phosphoenolpyruvate ADP Pyruvate Kinase CO2 + GDP PEPCK ATP GTP AminoAmino Acids Acids Pyruvate Lactate

NADH + H+ NAD+ Oxaloacetate

+ Malate NADH + H Pyruvate + Dehydrogenase NAD CO2 + ATP Pyruvate Carboxylase ADP + Pi

Malate Oxaloacetate Dehydrogenase NADH + H

NAD Citrate

Malate Malate + +

Pathways that flow through gluconeogenesis. Glucogenic precursors include Amino Acids lactate, pyruvate, glycerol, and glucogenic amino acids.

Pi Glucose ATP Glucose 6- There are three steps and four enzymes involved. HK phosphatase Glucose 6- Step 1 Pyruvate to Phosphoenolpyruvate (2 enzymes) H2O phosphate ADP Glycogen Pi Fructose 6-P ATP 1. Pyruvate carboxylase (PC) Fructose 1,6- PFK Bisphosphatase Fructose H2O 1,6 Bis P ADP • pyruvate + CO2 + ATP-> oxaloacetate + ADP +Pi • Pyruvate is carboxylated in the mitochondria and

the reaction is driven by ATP hydrolysis Phosphoenolpyruvate ADP Pyruvate Kinase CO2 + GDP PEPCK ATP GTP AminoAmino Acids Acids Pyruvate Lactate NADH + H+ NADTransport+ of OAA Oxaloacetate -inner mito membrane tight

+ - No transporters for OAA Malate NADH + H Pyruvate + - Malate can be transported Dehydrogenase NAD CO2 + ATP Pyruvate Carboxylase ADP + Pi Malate Oxaloacetate Malate has to be converted Dehydrogenase NADH + H back to OAA NAD Citrate Malate Malate + - Two isoforms of MDH are +

used – inAmino both Acids forward and reverse reactions Net result is zero for this step

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2. Phosphoenolpyruvate kinase (PEPCK) Pi Glucose ATP Glucose 6- HK •2 isozymes cytosolic/mitochondrial phosphatase Glucose 6- H2O phosphate ADP

•Found in liver, kidney and adipose Glycogen Pi Fructose 6-P ATP Fructose 1,6- PFK •OAA + GTP -> PEP + GDP + Pi Bisphosphatase Fructose H2O 1,6 Bis P ADP •Potential involvement in SIDS •In adipose (fat cells) glycerol is produce rather Phosphoenolpyruvate ADP than glucose (via - glycerol 3-phosphate). Used Pyruvate Kinase CO2 + GDP PEPCK ATP GTP for glycerol backbone of triacylglycerol AminoAmino Acids Acids Pyruvate Lactate

NADH + H+ NAD+ •In kidney PEPCK is responsible for decrease Oxaloacetate ammonia produced via the krebs cycle. Ultimately + StepMalate 2 FructoseNADH + H 1,6-bisphosphatePyruvate to fructose 6- responsible for acid base regulation,) + Dehydrogenase NAD CO2 + ATP phosphate Pyruvate Carboxylase ADP + Pi • Fructose 1,6Malate- bisphosphataseOxaloacetate (FBPase-1) Dehydrogenase • found in ofNADH + liverH and kidney a little in NAD Citrate

Malate Malate + striated muscle + Amino Acids • hydrolysis of 1-phosphate from fructose

Pi Glucose ATP Glucose 6- HK Regulation of phosphatase Glucose 6- H2O phosphate ADP Glycogen Gluconeogenesis Pi Fructose 6-P ATP Fructose 1,6- PFK Bisphosphatase Fructose H2O 1,6 Bis P ADP The regulation of gluconeogenesis is in many ways the reciprocal of

Phosphoenolpyruvate glycolysis. In addition, the first ADP Pyruvate Kinase two reactions of CO2 + GDP PEPCK ATP GTP gluconeogenesis are AminoAmino Acids Acids Pyruvate Lactate

NADH + H+ NAD+ compartmentalized to the Oxaloacetate mitochondria.

Step 3 Glucose+ 6-phosphate to glucose Malate NADH + H Pyruvate • Occurs through Dehydrogenase • glucoseNAD+ 6 phosphatase (G6Pase) CO2 + ATP compartmentalization Pyruvate Carboxylase • 5 subunit enzyme found inADP endoplasmic + Pi reticulum Malate Oxaloacetate • Allosteric regulation • Only in liverDehydrogenase and kidney • Hydrolysis of 6-phosphateNADH + H NAD Citrate • Phosphorylation

Malate Malate + • requires transport in and+ out of ER • Changes in gene • Von Gierkies Disease - missing G6PaseAmino Acids expression

Control of Gluconeogenesis Fates of Pyruvate

Several common factors that increase one pathway will shut off the other. – High energy state -> ATP, citrate – Low energy state -> ADP, AMP – Fructose 2,6 bisphosphate -> increase blood [glucose] – Starvation increases gluconeogenesis – High carbo reduces gluconeogenesis while low carbo increases. In general, the well feed state decreases gluconeogenesis and increases glycolysis Fates of pyruvate. There are five fates of pyruvate discussed in this section, four of which are carried out in animals (decarboxylation is only carried out by microbes, such as some yeast and ).

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