Metabolism of amino acids

Department of Biochemistry (J.D.) 2013

1 Intermediates of amino acid catabolism

• Glucogenic (13) pyruvate and/or CAC intermediates

• Ketogenic (2) = Leu, Lys acetyl-CoA + acetoacetate

• Mixed (5) = Thr, Ile, Phe, Tyr, Trp

2 Intermediates of amino acid catabolism

Ser,Ala, Cys,Gly, Gly,Thr, Ser, Ala, Thr, Cys, (Trp) Trp pyruvatepyruvát glucoseglukosa

Ile, Leu, Lys, Thr

acetyl-CoA acetoacetateacetoacetát Leu, Lys, Phe, Trp, Tyr Asp, Asn oxaloacetateoxalacetát CC Phe, Tyr fumarátfumarate 22-oxoglutarát-oxoglutarate Arg, Glu, Gln, His, Pro Asp succinylsukcinyl-CoA-CoA Ile, Val, Met, Thr

3 Alanine Transamination of alanine

2-oxoglutarát2-oxoglutarate

Gluglutamate

ALT

H 3 C C H C OOH H 3 C C C OOH alanine aminotransferase NH 2 O

alaninalanine pyruvátpyruvate

4 Glucose-alanine cycle

liver muscle

glucose glucose

glycolysis gluconeogenesis

pyruvate transport in blood pyruvate

transamination transamination alanine alanine

• alanine is non-toxic transport of ammonia from muscles to liver • in the liver, alanine is the substrate for gluconeogenesis 5 Alanine - summary

• readily made from pyruvate (transamination)

• ALT is clinically important enzyme, mainly in liver, elevated catalytic concentration in blood serum – liver diseases

• Ala is released to blood mainly from muscles, together with Gln (postresorption phase)

• semiessential AA (in metabolic stress) – important substrate for gluconeogenesis

6 Arginine no transamination

Hydrolysis of arginine urea

C H 2 C H 2 C H2 C HC OOH C H 2 C H 2 C H 2 C HC OOH NH NH NH 2 NH 2 2 ornitin C N H ornithine H 2 O

N H 2 N H 2 glutamate argininearginin C O N H 2 urea

7 NO is signal molecule from arginine

C H C H C H C HC OOH 2 2 2 C H 2 C H 2 C H 2 C HC OOH NH NH 2 NH NH 2 O , NA D P H C N H 2 C N O H NH 2 BH4 NH 2

NN-hydroxyarginin-hydroxyarginine Exogenous NO sources • glycerol trinitrate • isosorbide dinitrate O 2 , NA D P H • amyl nitrite • isobutyl nitrite

• sodium nitroprusside C H 2 C H 2 C H 2 C HC OOH + N O NH NH 2 oxidnitric dusnatý oxide (nitroxidradical radikál) C O citrulincitrulline 8 NH 2 Synthesis of creatine (1. part)

from Greek κρέας (meat)

C H2 C OOH C H2 C OOH

NH2 H2 N NH C glycinglycine NH guanidinoacetate

C H2 C H2 C H2 C H C OOH C H2 C H2 C H2 C H C OOH

H2N NH NH2 NH2 NH2 C

NH arginine ornithine

9 Synthesis of creatine (2. part) N1-methylation of guanidinoacetate

S-adenosylhomocysteine

S-adenosylmethionine (SAM) C H2 C OOH C H2 C OOH

H2 N NH H2 N N C C C H3

NH NH

guanidinoacetate creatine N-methylguanidine-N-acetate

10 N2-Phosforylation of creatine

C H2 C OOH O C H C OOH ATP H 2 H2 N N HO P N N C C H 3 C C H3 OH NH NH

creatinekreatin creatinekreatinfosfát phosphate

11 Creatinine is a catabolite of creatine made in non-enzymatic reaction

O C H C OOH non-enzymatic 2 C C H cyclization dehydratation 2 H N N 2 N N C C H3 H C C H3 NH - H O 2 NH kreatin creatine creatinine

12 Arginine - summery

• semiessential AA (childhood)

• the most basic AA (guanidine, pKB = 0.5) • no transamination, Arg releases ornithine + urea

• Arg + Gly + Met creatine

• releases NO (vasodilator)

• OTC (over-the-counter) preparations in pharmacy

13 Serine Dehydratation + deamination of serine

OH H

C H 2 C C OOH C H 2 C C OOH H 3 C C C OOH - H 2 O N H 2 N H 2 N H

enamineenamin imineimin

H 2 O

+ H C C C OOH N H 3 3 O pyruvatepyruvát

14 Conversion of serine to glycine

C H C OOH + H OC H F H C H 2 C H C OOH + F H4 2 2 4 NH OH NH 2 2

serinserine glycineglycin

H2O + N5N10-CH2-FH4 cofactor: methylene FH4 tetrahydrofolate (FH4)

15 Transamination of serine and glucose formation

2-oxoglutarate2-oxoglutarát Glu C OOH C OOH C OOH NADH + H + H 2 N C H C O C H OH

C H 2 OH C H 2 OH C H 2 OH

serineserin hydroxypyruvatehydroxypyruvát glycerátglycerate

ATP reverse reaction: synthesis of serine ADP pathway is different - through phosphoserine C OOH 3-P-glycerát3-P-glycerate glucoseglukosa C H OH O

C H 2 O P O 16 O Decarboxylation of serine gives ethanolamine. Methylation of ethanolamine leads to choline

decarboxylation methylation C H3

HO C H2 C H C OOH HO C H2 C H2 NH2 HO C H2 C H2 N C H3

NH2 C H3 serine ethanolamine choline

Betaine is made by choline oxidation

C H 3 C H 3 oxidation H O C H 2 C H 2 N C H 3 H OOC C H 2 N C H 3

C H 3 C H 3

choline betaine

17 Serine - summary • non-essential glucogenic AA • source of C1 fragments (attached to tetrahydrofolate) • component of glycerophospholipids • decarboxylation gives ethanolamine choline • carbon skeleton used for selenocysteine • serine side chain in proteins: the site of phosphorylation the linkage of oligosaccharides (O-glycoside bond) nucleophilic -OH group in active site of enzyme (serine proteases)

18 Glycine

The complete catabolism of glycine

+ N H C H 2 C O O H + F H 4 N 5 N 1 0 C H 2 F H 4 + C O 2 3

N H 2

C1 fragment (methylene) is transferred to tetrahydrofolate

19 Oxidative deamination of glycine

O O C C oxid. HO OH H O O O 2 oxalateoxalát C H 2 C OOH C H C OOH C C - NH 3 NH 2 NH H OH F A D F A D H 2 glyoxalát glyoxylate O - C O 2 C S C oA H H 2 O 2 O 2 formyl-CoA

60 % catabolism of glycine and ethanolamine 30 % catabolism of vitamin C 10 % food (spinach, rhubarb, mangold, tea, cocoa) 20 Glycine - summary

Catabolism Anabolic conversions • complete oxidation to • donor of C1 fragment • serine CO2 + NH3 • porphyrines • oxidative deamination • purine bases to oxalate • creatine • glutathione (GSH) • conjugation agent (bile acids, xenobiotics) 21

Threonine no transamination

Threonine (4C) is split to glycine (2C) and acetaldehyde (2C)

C OOH C OOH serinserine pyruvátpyruvate H 2 N C H 2

H 2 N C H glycineglycin H C OH O O C H 3 C H C C H 3 C 3 H S C oA acetaldehydacetaldehyde acetyl-CoA

• essential AA • two asymmetric C atoms

• the site of phosphorylation and glycosylation in proteins 22 Methionine no transamination

Methionine is methylation agent (homocysteine side product)

ethanolamine PP i + P i noradrenaline C H substratesubstrát 3 guanidinacetate

HOOC C H C H 2 C H 2 S Rib A d ATP NH 2 S-Sadenosylmethionine-adenosylmethionin

substratesubstrát -CCHH 33 C H 3 cholinecholin HOOC C H C H 2 C H 2 S adrenalinadrenaline HOOC C H C H 2 C H 2 S Rib A d creatinekreatin NH 2 NH 2 S -adenosylhomocystein methioninemethionin

remethylationremethylace HOOC C H C H C H S H F H 4 2 2 B NH 2 12 homocysteinehomocystein 23 C H 3 F H 4 S-Adenosylmethionine (SAM) contains trivalent positively charged sulfur atom

NH2

N N

N N C H 3 S HOOC C H C H2 C H2 O NH 2

cation - sulfonium OH OH 24 Cysteine is made from methionine

methionine HOOC C H C H 2 C H 2 S H

NH 2 homocysteinehomocystein pyridoxal-P kondenzacecondensation se serinem with serine H 2 O

HOOC C H C H 2 C H 2 S C H 2 C H C OOH NH 2 NH 2 cystathioninecystathionin

C H2 C H C OOH odštěpenícysteine cysteinu release S H NH2

HOOC C H C H 2 C H 2 OH B12 cysteine succinyl-CoA NH 2 homoserinehomoserin 25 Methionine - summery

• essential AA, rather rare in foodstufs

• S-adenosylmethionine (SAM) is methylation agent

• metabolized to cysteine Cys is non-essential AA

• C-skeleton of cysteine comes from serine, sulfur atom from methionine

• final catabolite is succinyl-CoA (glucogenic)

26 Homocysteine is harmful

• mechanism of its action is not yet understood • direct action on blood vessel epithelium • decreases thrombocyte life and fibrinolysis • supports formation of oxygen radicals – damage of vessel wall • increases LDL lipoperoxidation • elevated blood level of homocysteine is risk factor of cardiovascular diseases to eliminate homocysteine - three vitamins are needed: folate, cobalamine, pyridoxin

27 Cysteine Cysteine catabolism: oxygenation of -SH group C OOH C OOH C OOH H 2 N C H H N C H oxygenationoxygenace oxygenation 2 H 2 N C H C H 2 C H 2 O 2 C H 2 S H S O S O O OH OH cysteinecystein cysteinecysteinsulfinát sulfinate cysteovácysteic kyselina acid dekarboxylacedecarboxylation

transaminationtransaminace

C OOH H 2 N C H 2 oxygenationoxidace H 2 N C H 2 O C C H 2 C H 2 C H S O S O 2 O OH S OH O OH hypotaurinehypotaurin taurinetaurin sulfinylpyruvátsulfinylpyruvate 28 The formation of sulfite

C OOH C OOH hydrolytic hydrolytické O C O C odštěpenícleavage sulfitu of sulfite C H 3 H 2 O C H 2 pyruvátpyruvate S O OH OH O sulfinylpyruvátsulfinylpyruvate + 2 H S S O OH O O

sulfit (siřičitan)sulfite

- under physiol. pH – dissociation only to HSO3 29 Sulfite oxidase catalyzes sulfate formation

NH 2

N O N O S O O N N O P O O O cysteine PAPS

O O OH P O O

- 2- + - HSO3 + H2O SO4 + 3H + 2e

blood plasma acidify (0.5 mmol/l) body fluids reduce molybdopterine

30 urine Distinguish

2- Sulfite anion SO3

Sulfide inorganic anion S2- (e.g. ZnS zinc sulfide)

Sulfide organic R-S-R dialkylsulfide

2- Sulfate anion SO4

31 Transamination of cysteine and sulfane production

22-oxoglutarát-oxoglutarate

glutamateGlu C OOH C OOH

H 2 N C H O C C H 2 C H 2 S H S H cystein cysteine merkaptopyruvátmercaptopyruvate

desulfuracedesulfuration

2- SO 2- H 2 S C OOH SO4 3 O C CN- sulfhemoglobin C H 3

- pyruvát signal molecule ? SCN pyruvate in smokers 32 Cysteine - summary

• both pathways go to pyruvate (glucogenic) • main catabolism: sulfur oxygenation sulfite sulfate • high protein diet leads to physiologic acidosis • cystein provids taurine – conjugation agent (e.g. bile acids) • taurine is semiessential AA in metabolic stress • taurine is a component of „energy drinks“ • cysteine – part of glutathione (GSH) - antioxidant • decarboxylation of Cys – cysteamine, in CoA-SH • in proteins – disulfide bonds (tertiary structure) • cysteine proteases: active site contains –SH group

33 Six amino acids provide pyruvate

1. Serine – dehydratation + deamination 2. Glycine – via serine 3. Threonine – via glycine 4. Alanine – transamination (ALT) 5. Cysteine – both catabolic pathways

6. Tryptophan – via alanine (see later)

34 Aspartate

• Transamination of Asp oxaloacetate (CAC)

• AST (aspartate aminotransferase) – clinically important enzyme

• in urea cycle, Asp donates one nitrogen into urea and releases fumarate

• decarboxylation of Asp β-alanine (part of coenzyme A)

• donor of nitrogen in purine synthesis (fumarate released)

• whole structure given for pyrimidine bases synthesis

• aspartam (sweetener)

• condensation with ammonia asparagine (for cell utilization, not as detoxication of ammonia)

35 β-Alanine is made by the decarboxylation of aspartate

β α H OOC C H C H H OOC C H 2 C H C OOH 2 2 - CO 2 N H N H 2 2

in the structure of CoA-SH

36 Glutamate

Glutamate with oxaloacetate afford aspartate (transamination)

oxaloacetateoxalacetát

aspartateAsp urea

AST

HOOC C H 2 C H 2 C H C OOH HOOC C H 2 C H 2 C C OOH

NH 2 aspartate aminotransferase O

glutamátglutamate 2-oxoglutarát2-oxoglutarate

AST reaction produces aspartate for urea synthesis

37 Dehydrogenative deamination of glutamate is the main producer of ammonia in tissues

glutamate dehydrogenase (GD, GDH, GMD)

HOOC C H C H 2 C H 2 C OOH HOOC C C H 2 C H 2 C OOH N H N H 2 NA D+ NA DH H+

glutamátglutamate 22-iminoglutarát-iminoglutarate

H 2 O

+ N H 3 HOOC C C H 2 C H 2 C OOH O 2-oxoglutarate2-oxoglutarát (CAC) 38 Decarboxylation of glutamate

HOOC C H2 C H2 C H C OOH HOOC C H2 C H2 C H2 - C O 2 NH2 NH2

GABA glutamátglutamate gama-aminobutyric acid

39 Glutamate - summary

• produced in the transaminations of most AA

• glutamate dehydrogenase reaction produces most ammonia in body

• transaminations are reversible, so glutamate can be converted to 2-oxoglutarate (glucogenic)

• Glu + NH3  Gln (ammonia detoxification) • glutamate is readily made from glutamine, histidine, proline, ornithine

• pure monosodium glutamate (MSG, E621), flavour enhancer, can cause health problems (chinese restaurant syndrome)

40 Glutamine

See also the previous lecture (AA-1)

• glutamine synthesis is the way of ammonia detoxification in tissues

including liver

• in kidneys, glutamine releases ammonia (deamidation)

• metabolic fuel for some tissues (enterocytes, fibroblasts, lymphocytes,

macrophages)

• donor of nitrogen for syntheses (glucosamine, purines)

41 Three amino acids donate four N atoms in purine bases synthesis

glycinglycine

N aspartateaspartát N

N N fumarate H amidováamide skupina group glutaminuof glutamine

amidováamide skupina group glutaminuof glutamine glutamate

42 Proline no transamination

Proline is converted to glutamate (and vice versa)

H C OOH C OOH N - 2H H N H pyrrolin-5-karboxylátpyrroline-5-carboxylate prolinproline addition of H O ad ice H 2 O 2 otevřeníring opening kruhu

oxidaceoxidation O C HOOC H C OOH C OOH H N H 2 N H glutamateglutamát glutamateglutamát-5-semialdehyd 5-semialdehyde 43 Hydroxylation of proline with 2-oxoglutarate as reductant

H C OOH O C C H O O 2 N C OOH C H2 H proline C OOH Fe2+ 2-oxoglutarate ascorbate - CO2

OH HO O C

C H2 N C OOH C H2 C OOH H 44 succinate 4-hydroxyproline Proline - summary

• non-essential AA, can be formed from glutamate

• converted to glutamate (glucogenic)

• hydroxylation of proline in collagen is post-translation modification,

requires ascorbate (vitamin C), Fe2+, and 2-oxoglutarate

(unusual co-reductant)

• 4-hydroxyproline is catabolized to pyruvate (see Harper)

45 Histidine no transamination

Catabolism of histidine starts with desaturation and deamination

N N CH CH COOH CH CH COOH N - NH3 N H H NH2 H urocanic acid (urocanate)

46 Urocanate cleavage affords C1 fragment O H 2 O CH C H C addition1. adice vodyof water 2. přesmyk N O H oxidative ring splitting C OOH N 3. oxid. otevření cyklu NH C HHCOH C OOH C H 2 C H 2 C OOH N 2 N N H H H urokanát urocanate NN-formiminoglutamát-formiminoglutamateFIGLU (Figlu)

F H 4

HN C H F H 4

HOOC

C H C H 2 C H 2 C OOH

H 2 N glutamát glutamate 47 Decarboxylation of histidine histamine

C H 2 C H C OOH C H2 C H 2 NH 2 N N NH 2

N N - CO2 H H histidine histamine

• histidine decarboxylase occurs in mast cells and basophils • histamine stimulates HCl production in stomach • is released in allergic reactions • triggers inflammatory response • antihistaminics are drugs blocking the action of histamine 48 Histidine is responsible for buffering actions of proteins

His H His N N H

N H N H H

pK (His) = 6 pKB = 8 A

pKA (His in proteins) = 49 6 -8 Histidine - summary

• semiessential AA • no transamination, catabolism begins with desaturation and deamination • the source of 1C groups (formimino) • converted to glutamate (glucogenic) • histidine is abundant in hemoglobin – buffer system • post-translation modification: methylation of His in actine/myosine 3-methylhistidine – its urine excretion is the indicator of muscle proteolysis and nutrition status

50 Leucine, Isoleucine, Valine (BCAA)

Leucine (1) - transamination + decarboxylation

H 3 C transaminationtransaminace H 3 C C H C H 2 C H C OOH C H C H 2 C C OOH H 3 C N H 2 H 3 C O

2-oxokybranched selina 2 -(2-oxoisokaproát)oxoacid

oxidative oxidační -C O 2 dekarboxydecarboxylation lace

H 3 C

C H C H 2 C S C oA

H 3 C O

branchedrozvětvený acyl acyl-CoA (isovaleryl-CoA) 51 Leucine (2) - dehydrogenation

H 3 C 2,32,3-dehy-dehydrogenation drogenace H 3 C C H C H 2 C S C oA C C H C S C oA

H 3 C O H 3 C O

rozvětvený nenasycený branched unsaturated acyl F A D F A D H 2 acyl

-methylkrotonyl-CoA)

52 Leucine (3) – carboxylation at C4

H C 3 carboxylationkarboxy lace HOOC C H2 C C H C S C oA C C H C S C oA H C 3 O H3 C O

acylacyl dikarboxylové of dicarboxylic rozvětvené nenasycenébranched unsaturated kyseliny acid ( -methylglutakonyl-CoA)

53 Leucine (4) – hydratation of double bond

OH HOOC C H 2 1 2 H2 O 3 C C H C S C oA HOOC C H2 C C H2 C S C oA

H3 C O C H3 O

3-hydroxy-3-methylglutaryl-CoA

(HMG-CoA)

54 Leucine (5) – splitting the C-C bond in HMG-CoA

OH

HOOC C H 2 C C H 2 C S C oA

C H 3 O

HMG-CoA-lyasaHMG-CoA lyase

HOOC C H 2 C C H 3 H 3 C C S C oA O O

acetoacetátacetoacetate acetyl-CoA 55 Compare the final products of BCAA

Leucine acetyl-CoA + acetoacetate ketogenic

B12 ketogenic Isoleucine acetyl-CoA + succinyl-CoA glucogenic

B12 Valine succinyl-CoA glucogenic

56 BCAA - summery

• all BCAA are essential

• the first three reactions are the same (transamination, oxid. decarboxylation, dehydrogenation), final products are different

• leucine – ketogenic, valine – glucogenic, isoleucine – mixed

• after meal, BCAA make about 70 % of AA in blood, because the liver does not utilize them (lack of aminotransferases)

• BCAA are most utilized in muscles and brain

• BCAA infusion are applied in severe catabolic conditions

57 Lysine no transamination Lysine catabolism (1)

HOOC C H (C H2 )4 N H 2 O C (C H 2 )2 C OOH

NH2 C OOH lysinlysine 2-oxoglutarát2-oxoglutarate

- H2 O

HOOC C H (C H 2 )4 N C (C H 2 )2 C OOH

NH2 C OOH

ketiminketimine (Schiffova (Schiff báze) base) 58 Lysine catabolism (2)

ketimine HOOC C H (C H 2 )3 C H 2 N C (C H 2 )2 C OOH ketim in

NH 2 C OOH

hydrogenacehydrogenation (NADPH)

HOOC C H (C H 2 )3 C H 2 N H C H (C H 2 )2 C OOH ssaccharopineach aro p in

NH 2 C OOH

dehydrogenacedehydrogenation (NAD)

HOOC C H (C H 2 )3 C H N C H (C H 2 )2 C OOH aldaldimineim in

NH 2 C OOH 59 Lysine catabolism (3)

HOOC C H (C H 2 )3 C H N C H (C H 2 )2 C OOH aaldimineld im in

NH 2 C OOH

hydrolytickéhydrolysis štěpení

O H 2 N C H (C H 2 )2 C OOH HOOC C H (C H 2 )3 C C OOH NH 2 H

allysineallysin glutamateglutamát 60 Lysine catabolism (4)

O OH H 2 O HOOC C H (C H 2 )3 C HOOC C H (C H 2 )3 C OH

N H 2 H N H 2 H

allysinallysine + dehydrogenationdehydrogenace ( N A D )

O

HOOC C H (C H 2 )3 C

N H 2 OH

22-aminoadipát-aminoadipate

61 Lysine catabolism (5)

glutamate 22-oxoglutarát-oxoglutarate Glu

O O

HOOC C H (C H 2 )3 C HOOC C (C H 2 )3 C

N H 2 OH O OH transaminationtransaminace 2-oxoadipate 2-aminoadipát2-aminoadipate 2-oxoadipát

- 2 CO 2

2 Acetyl-CoA

62 Lysine is the substrate for carnitine (the transfer of FA from cytosol to mitochondria)

COO COO

CH2 CH3 O CH2 CH3

HO CH CH2 N CH3 C O CH CH2 N CH3

CH3 CH3 carnitinekarnitin acylcarnitineacylkarnitin

63 Cross-links in collagen

products of reaction between the amino groups in side chains of lysine with the modified lysine side chains comprising the aldehyde group (the result of oxidation of lysine to allysine) – aldol type or aldimine type of cross-links.

O CO C H CO

HC(CH2)2 C CH (CH2)3 CH NH NH allysineallysin - H2O dehydratedpříčná vazba vzniklá aldol CO , CO dehydratací aldolu O2 H2O O HC(CH2)4NH2 HC(CH2)3 C H NH NH + NH3 H2O2 lysinlysine + + CO CO hydrogenationhydrogenace HC(CH2)4 NH (CH2)4 CH lysinelysin allysineallysin (lysylový zbytek v polypeptidu) NH NH (lysyl residue in polypeptide) hydrogenated příčná vazba aldiminevzniklá hydrogenací Schiffovy báze64 Formation of fibrin clot during blood coagulation (cross-linking of fibrin)

O + Fibrin C H C H C H C H NH C H 2 2 2 2 3 H 2N C C H 2 2 Fibrin

lysine glutamine + NH 4

O C H NH C C H C H Fibrin C H 2 C H 2 C H 2 2 2 2 Fibrin

cross-linking 65 Lysine - summary

• essential AA, no transamination • ε-amino group is removed as glutamate • -amino group is removed from aminoadipate by transamination • final product acetyl-CoA (ketogenic) Other conversions: • lysine in many proteins binds ubiquitin (targeting for proteasome) • carnitine (transport system for FA to mitochondria) • decarboxylation cadaverine • in collagen: cross bridges, hydroxylation hydroxylysine • in fibrin: cross linking during blood coagulation 66 Phenylalanine, Tyrosine Catabolism (1)

C OOH C OOH C OOH

H2 N C H H 2 N C H C O hyhydroxylation droxy lace transaminacetransamination C H C H 2 2 C H2 O 2 , B H4

OH OH

phenylalaninefenylalanin tyrosinetyrosin p-hydroxyphenylpyruvatep-hydroxyfenylpyruvát

67 Catabolism (2)

C OOH oxidative1. oxid. dekarboxylacedecarboxylation C O OH rearrangement2. přesmyk C H C H 2 C OOH 2 hydroxylation3. hydroxylace

- C O 2 OH

OH homogentisáthomogentisate (2,5-dihydroxyfenylacetát) p-hydroxyphenylpyruvate (2,5-dihydroxyphenylacetate)

68 Catabolism (3)

O O

OH O C OH C H2 C OOH dioxygenase

oxidative cleavage C OOH of aromatic ring OH O O

maleinylmaleylacetoacetateacetoacetát

69 Catabolism (4)

C OOH HOOC isomerationizomerace

C OOH C OOH

O O O O maleinylacetoacetátmaleylacetoacetate fumaroylacetoacetátfumarylacetoacetate

70 Catabolism (5)

HOOC H 2 O HOOC

H 3 C C OOH C OOH C OOH O O O

fumaroylacetoacetátfumarylacetoacetate fumaratefumarát acetoacetateacetoacetát

71 Hyperphenylalaninemia and Phenylketonuria

C OOH C OOH • deficit of hydroxylase or BH4

H2 N C H H 2 N C H hydroxylasahydroxylase • elevated blood Phe and its C H2 x x x C H 2

O 2 , B H 4 metabolites

• excretion of phenylpyruvate by urine OH

phenylalaninefenylalanin tyrosintyrosine

72 Metabolites of phenylalanine

C OOH

C H 2

C OOH C OOH oxid. oxid. H N C H decarboxylationdekarboxy lace 2 transaminationtransaminace C O

C H 2 C H 2 phenylacetatefenylacetát

C OOH hydrogenationhy drogenace C H OH

C H 2 phenylalaninefenylalanin phenylpyruvatefenylpyruvát

phenyllactatefenyllaktát 73 Hyperphenylalaninemia and Phenylketonuria

• if not treated properly – mental retardation and other problems • treatment – low phenylalanine diet • products containing sweetener aspartam must be avoided • L-aspartyl-L-phenylalanine methyl ester - phenylalanine is released by hydrolysis: HOOC H O

N C H 3 H 2 N O O

74 Hydroxylation of phenylalanine gives tyrosine

C OOH C OOH

H 2 N C H + H N C H + H O + + O O B H 4 2 2 B H 2

C H 2 C H 2

co-reductant tetrahydrobiopterine

H OH phenylalanine tyrosine

75 Tyrosine DOPA and dopamine from tyrosine

C OOH C OOH NH 2

C H 2 H 2 N C H H 2 N C H hyhydroxylation droxy lace decarboxylationdekarboxy lace C H 2 C H 2 C H 2 O 2 , B H 4 - CO 2

OH OH OH OH OH

tyrosinetyrosin DOPA dopamindopamine (3,4-dihydroxyfenylalanin)(3,4-dihydroxyphenylalanine) (catecholamine)(katecholamin)

76 Linguistic note

• abbreviation DOPA comes from older English nomenclature

• oxo group and hydroxyl group were not distinguished properly:

DOPA = dioxophenylalanine

• correct chemical name is: 3-(3,4-dihydroxyphenyl)alanine

77 Two more catecholamines from dopamine

NH 2 NH2 NH C H 3 C H hyhydroxylation droxy lace na C-2at C2 NN-methy-methylation lace 2 C H2 C H2

C H2 C H OH C H OH OO22,, aascorbatesko rbá t SAM Cu2+

OH OH OH OH OH OH dopamindopamine noradrenalinnoradrenaline adrenalinadrenaline

nor- = N-demethyl 78 Conversion of tyrosine to melanin, a dark pigment of skin, hair, fur

HO O condenzation N H 2 NH 2

O H O H melanin O C HO C - 2H O O

DOPA dopaquinone

79 Conversion of tyrosine to thyroxine

I

2 I HO C H C HC OOH 2 HO C H 2 C HC OOH

NH 2 NH 2 I tyrosin tyrosine 3’,5’3',5'-dijodtyrosin-diiododtyrosine bound to I thyreoglobulin HO C H 2 C HC OOH

NH 2 I I I

HO O C H 2 C HC OOH

NH 2 I I

thyroxinthyroxine 80 Phenylalanine, tyrosine - summary

• Phe is essential amino acid, Tyr not

• Tyr is made by Phe hydroxylation (tetrahydrobiopterine cofactor)

• catabolism is the same for both AA (mixed AA)

• provide fumarate for CAC (glucogenic)

• acetoacetate (ketone body)

• tyrosine is converted to hormones (catecholamines, thyronines) and dark skin pigment melanin

81 Tryptophan no transamination

Catabolism (1)

C H2 C H C OOH C H2 C H C OOH NH2 C NH 2 oxidativeox ida č ncleavageí O of aromaticrozště pe n ringí O N NH C H O2 H tryptophantryptofan NN-formylkynurenin-formylkynurenine

82 Catabolism (2)

C H 2 C H C OOH C H 2 C H C OOH C NH 2 hydrolysis of C O hydrolýza amidu NH 2 O amide group O NH C H O + HCOOH 2 NH H 2 kynurenin formate amid mravenčí kyselinyformamide

hydroxylacehydroxylation

C H 2 C H C OOH C NH 2 O

NH 2 OH

3-hydroxykynurenin 83 Catabolism (3)

H 2 O H 3 C C H C OOH C H 2 C H C OOH C NH 2 NH 2 hydrolytic hydrolytické cleavage Ala O odštěpeníof alanine alaninu

NH 2 C OOH OH

3-hydroxykynurenin NH 2 OH

33-hydroxyanthranilát-hydroxyanthranilate

84 Catabolism (4)

C OOH

NH 2 OH 33-hydroxyanthranilát-hydroxyanthranilate

3 % 97 %

O O H 3 C C C ONH HOOC 2 C OOH S C oA 22-oxoadipát-oxoadipate acetyl-CoA N nicotinamidenikotinamid 85 Decarboxylation of tryptophan

CH2 CH COOH CH2 CH2 NH2 NH2

N - CO N H 2 H tryptophan tryptofan tryptamintryptamine

86 Conversion of tryptophan to melatonin

CH2 CH COOH CH CH COOH 2 CH2 CH2 NH2 HO NH HO 2 NH2 hydroxylationhydroxylace decarboxylationdekarboxylace N N N H H H BH BH tryptofanTrp 4 2 5-hydroxytryptofan5-hydroxytryptophan serotonin

acetylaceN-acetylation methylaceO-methylation

CH2 CH2

H3C O sleep-wake cycle NH C CH3 O N the hormone of darkness H melatonin

87 Tryptophan - summary

• essential AA

• complicated catabolism

• donor of 1C fragment (formic acid - formate)

• no transamination, amino group leaves as alanine (glucogenic)

• final product acetyl-CoA (ketogenic)

• source of nicotinamide and NAD+

• bacterial decomposition in large intestine indole and skatole (3-methylindole) – exhibit strong fecal odor

88 Five vitamins are formed in the body, only four are utilized

Vitamin Where and how produced

Niacin in tissues, from tryptophan

Biotin large intestine (bacteria)

Phylloquinone large intestine (bacteria)

Calciol skin, from cholesterol (UV radiation)

Cobalamine large intestine (bacteria) – not absorbed!

89 Seven amino acids do not undergo transamination

Amino acid -NH2 group is removed as Arginine ornithine Lysine 2-aminoadipate Methionine homoserine

Threonine glycine Tryptophan alanine Proline glutamate

Histidine NH3 (desaturation deamination) 90 AA Biochemically relevant product

Ala pyruvate glucose Arg urea, NO, creatine Ser ethanolamine choline betaine; donor of 1C fragment, selenocysteine Gly heme, creatine, GSH, conjugation reagent (e.g. glycocholate) Met donor of methyl, creatine, homocysteine, cysteine 2- Cys glutathione (GSH), taurine, SO4 , PAPS, cysteamine (CoA)

Asp donor of -NH2 (urea, pyrimidines), oxaloacetate, fumarate, β-alanine (CoA) + Glu NH4 , 2-oxoglutarate, GABA, ornithine + Gln NH4 , donor of -NH2 (synthesis of glucosamine, purines) Pro glutamate, hydroxyproline His glutamate, histamine, donor of 1C fragment Lys glutamate, allysine (collagen), carnitine, cadaverine Tyr fumarate, catecholamines, thyroxine, melanins Trp nicotinamide, serotonin, melatonin, donor of 1C fragment, indole, skatole

91 Overview: decarboxylation of amino acids AA Product Comments Ser ethanolamine part of phospholipids, precursor of choline Cys cysteamine part of coenzyme A (CoA-SH) Phe phenethylamine structural part of stimulants (amphetamine, ephedrine etc.) Tyr tyramine occurs in some foods, may cause migraine Asp -alanine part of pantothenic acid, CoA-SH, carnosine Glu GABA gama-aminobutyric acid, inhibition neurotransmiter Lys cadaverine product of putrefaction (decay of proteins) Arg agmatine signal molecule in CNS His histamine triggers allergic reactions Trp tryptamine precursor of serotonine and melatonine DOPA dopamine catecholamine, precursor of noradrenaline/adrenaline Ornithine putrescine putrefaction product; precursor of spermidine/spermine

92