PETER PAZMANY CATHOLIC UNIVERSITY

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Development of Complex Curricula for Molecular Bionics and Infobionics Programs within a consortial* framework**

Consortium leader

PETER PAZMANY CATHOLIC UNIVERSITY

Consortium members

SEMMELWEIS UNIVERSITY, DIALOG CAMPUS PUBLISHER

The Project has been realised with the support of the European Union and has been co-financed by the European Social Fund ***

**Molekuláris bionika és Infobionika Szakok tananyagának komplex fejlesztése konzorciumi keretben

***A projekt az Európai Unió támogatásával, az Európai Szociális Alap társfinanszírozásával valósul meg.

PETER PAZMANY CATHOLIC UNIVERSITY SEMMELWEIS

UNIVERSITY

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BIOCHEMISTRY

Semmelweis University

Metabolism of amino acids

www.se.hu

(Aminosavak metabolizmusa)

Raymund Machovich

http://semmelweis-egyetem.hu/

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Lecture objectives To learn:

1) Amino acids necessary for biological systems: essential and nonessential amino acids 2) The source of nitrogen, and its incorporation into amino acids

3) The functions of amino acids: formation of molucules containing nitrogen, protein synthesis, energy

4) Uptake of amino acids by human: degradation of proteins by preoteases present in the gastro-intestinal tract

5) Controls of digestive enzyme activities: proenzymes and their activation, and the inhibitor system

6) Degradation of proteins in the blood and in the cells and amino acid transport

7) General reactions in amino acid metabolism: glutamate dehydrogenase, amino transferases, one-carbon transfer (tetrahydrofolate and S-adenosylmethionine)

8) Biosynthesis of nonessential amino acids: Cys, homocystein, Tyr and Phenylketonuria (PKU) 9) Degradation of amino acids: fate of carbon skeleton and the nitrogen (the ornitine cycle)

10) Catabolism of Ile, Thr, Met, Val: functions of Vitamin B

11) Thyroxin formation and action

Biochemistry: Amino acids

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Biochemistry: Amino acids

www.se.hu http://semmelweis-egyetem.hu/

Amino acid metabolism

Protein

synthesis Energy Nitrogen metabolism

Amino acids

Synthesis of nonessential

Protein digestion

Synthesis of essential amino acids Degradation

Uptake transport

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Biochemistry: Amino acids

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Amino acids

Nonessential: 17 enzymes Ala

Asp Asn Cys Glu Gln Gly Pro Ser Tyr

Posttranslation Gla

Hyl Hyp

Semiessential Arg

Essential: 59 enzymes Arg

His

Ile Leu Lys Met Phe Thr Trp Val

+ Slow synthesis at children

5

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Fe

Lys-hydroxylase Vitamin C Lys

O

CO

Carbohydrate side chains (collagen) α-keto-

glutarate succinate

- N – C – C - CH

CH

H –C - OH

CH

H O

NH

5 - Hyl

scurvy

C = O COO^-

C = O O^-

O₂ Fe³⁺

Enzyme – Fe²⁺

Vit-C reduction

Biochemistry: Amino acids

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Pro

Pro-hidroxylase Vitamin C

Collagen stability (Tm)

Deficiency in vessel wall: „fragility”

Ageing: lost elasticity

- N – C – C - CH

H O

H

C

HC – O H 4-Hyp

Fe

O ₂ CO ₂

α-keto-

glutarate succinate

Biochemistry: Amino acids

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CO

Carboxylase

Vitamin K

(cofactor for Carboxylase)

OH

CH₃

R OH

hydroquinone

O

H

O

epoxide

Dehidrogenase NADPH quinone

Reductase Coumarins

--

CH

CH

COOH

Glu Gla

CH

H C - COOH COOH

γ

Biochemistry: Amino acids

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Nitrogen fixation

Nitrogen enters in reduced form into the synthesis of amino acids:

N N + 3H ₂ 2NH ₃ N N + 3H ₂ 2NH ₃

Nitrogenase (in biological system) Mr ≈ 220 000

NADH NAD Ferredoxin

6 e

Reductase

SH Fe

Mo -protein

N

2NH

12 ATP 12 H₂O 12ADP 12 Pi 4 H⁺

Iron catalyst 500 C°

300 atm (atmosphese:: 0.03 atm)

Only a few species of microorganisms can fix atmospheric nitrogen (e.g. cyanobacteris, soil bacteria, some algae)

Biochemistry: Amino acids

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Ammonia is incorporated into glutamate (Glu) and glutamine (Gln)

COOH C O CH

CH

COOH

=

α-keto glutarate

NH

H

O

Glutamate

dehydrogenase NADPH

COOH C NH

CH

CH

COOH H

+

Biochemistry: Amino acids

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Gln NADPH

NADP

Glutamate synthase

(in procaryotes)

2Glu

Glutamine

synthetase _ADP

Pi COOH

C NH

CH

CH

C – NH

H

O =

ATP

NH

Biochemistry: Amino acids

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Proteins as energy source

≈40g/day (1-2 g essential amino acids) 70kg human

≈ 30 g

for synthesis of protein and molecules containing nitrogen

≈ 10 g for degradation

Protein starvation: 30g/day Kwashiorkor (protein)

Marasmus (protein + energy)

Biochemistry: Amino acids

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Energy stores (kJoule)

250 190 0

Liver 1700 1900 1700

Brain 30 0 0

Muscle 5000 1900 100800

Lipid tissue 300 570000 170

Glycogen Lipid Protein

Blood

Biochemistry: Amino acids

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Serine proteases

O

C N

H H

O H

R

R

H O

Ser His

O

HO C R

═

NH

R

ε

N

Biochemistry: Amino acids

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O

C N

H H

O

H

Zn²⁺

Glu C = O O

Zinc protease

(Carboxypeptidase A)

Asp O = C Asp

O C = O

OH

Carboxyl protease (pepsin, lysosome virus AIDS virus)

Cys S

Thiol protease

(papain, cancer procoagulant)

Other proteases

Biochemistry: Amino acids

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Protein digestion

Proteins are hydrolysed for peptides and amino acids in the gastrointestinal tract

In stomac:

Pepsin: Mr = 35 000, acidic protease

(pH 1-2) ,

It digest primarily denatured proteins at Tyr and Glu.

(The low pH is necessary for enzyme action and substrate denaturation) The result: large peptide formation

+

Carboxyl protease

Biochemistry: Amino acids

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Protein digestion

In Intestine:

Trypsin

Mr = 25 000, pH optimum: 7.5-8.5.

Peptide bonds are hydrolysed at Arg and Lys Chymotrypsinogen is activated by trypsin Chymotrypsin* Mr = 25 000, endopeptidase Peptide bonds are hydrolysed at Phe, Trp, Tyr

Elastase *

Mr = 30 000, endopeptidase.

Elastase is not specific for elastin. It hydrolyses Gly, Ala, Ile.

Carboxypeptidase –A

Mr = 30 000, C-terminal amino acids are recognised

* Serine protease + zinc protease

o pancreas PMN

Biochemistry: Amino acids

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Controls of digestive enzyme activities

Gastrointestinal proteases are synthesized primarily in precursore form (zymogen, proenzyme)

Destructions by proteases is prevented by inhibitor system

Biochemistry: Amino acids

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Proenzyme activations

AC AC

C

A AC

Biochemistry: Amino acids

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Activation of pepsinogen

Pepsinogen (Mr 40 kDa) is produced in the stomac

Asp Asp

Lys Lys Arg

Asp Asp

pH < 5

Pepsinogen pH = 7

Leu -Ile

Asp

Asp

Asp Asp

Pepsin

Leu

Ile

Biochemistry: Amino acids

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Activation of pancreas proenzymes

Trypsinogen, Chemotrypsinogen, proelastase and procarboxypeptidase are synthesized and

stored in the pancreas in together with α

– protease inhibitor (α

- antitrypsin) and trypsin inhibitor

Stomac content

Cholecystokinin (pancreozymin)

Pancreas

Duodenum Entero peptidase

Biochemistry: Amino acids

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Trypsinogen

N-Val-Asp-Asp-Asp-Asp-Lys-Ile-Val His

Asp

Ser

Ile-Val

Ser His

Asp

Trypsin

Conformational alteration

Enteropeptidase

Biochemistry: Amino acids

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Pancreas proenzymes are activated by trypsin Trypsin

1 Arg –Ile

His Ser 245

s s

Chymotrypsinogen Proelastase

Procarboxy peptidase

Elastase

Carboxypeptidase

Ile Ser

His

Asp s

s

Chymotrypsin Arg

Acute pancreatitis, Absorbtion problems

Asp

Biochemistry: Amino acids

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Pancreas trypsin inhibitor (PTI)

Active center of trypsin is bound to the inhibitor (Mr ≈6 000) by high affinity (Kd ≈10

M) One peptide bond is hydrolysed (Lys

– Ala

) in PTI, but the rate of hydrolysis is slow:

The half-life of complex is sveral months

PTI Lys-Ala Asp – His - Ser

Trypsin

O = C – O

Asp

NH

PTI Lys

-Ala

Biochemistry: Amino acids

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α

-Protease inhibitor (α

PI) (α

-antitrypsin)

The most significant inhibitor of the elastase. Its blood plasma level is >20μM, an acute phase protein (Mr ≈53 000). A covalent bond is formed between the hydroxyl group of active centers serine of the enzyme and

a carboxyl group of the inhibitor.

The inhibitor Met

is necessary to the binding with the enzyme.

Enzyme Ser - OH

HO - C O

Met

α ₁ PI

At smokers the Met is oxidized to methionine sulphoxide

Met –CH

–S - CH

Met –CH

–S - CH

O

PMN: Elastase + myeloperoxidase

Met Arg

α

PI AT

40μM 4μM α

Biochemistry: Amino acids

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Tissue proteinases

They play a role in throphoblast implantation, embrio morphogenesis,

tissue remodelling, angiogenesis, bacterial invasion and tumor metastasis formation.

They are produced by macrophages, neutrophils and endothelial cells.

Biochemistry: Amino acids

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TIMP ( Tissue inhibitors of metalloproteinases – 1 – 4 ) play a role in:

Rheumatoid arthritis Atherosclerosis

Tumor metastasis Aortic aneurysm

Biochemistry: Amino acids

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Matrix metalloproteinases (MMP)

Zn

Propeptide

Cys FN Catalytic HP Transmembrane

Activation:

Zn S- Zn -SH

MMP

Zn

Proenzyme Intermedier Enzyme

FN: Fibronectin-like repeate HP: Hemopexin

P NO

Biochemistry: Amino acids

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Zn

Zn

Zn

Zn

MP-7

MP-1, MP-8 MP-3, MP-10 MP-2, MP-9

Membrane- metalloproteinase MP-14, MP-15, MP-17

Biochemistry: Amino acids

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Procollagen

s

s s

s

Peptidase „Ehlers-Danlos”

syndrome

Flexible joint, skin

superhelix Intracellular

Collagens

Fibroblast

Biochemistry: Amino acids

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Extracellular Tropocollagen

39% Gly 1 Gly mutation

„Osteogenesis imperfecta”

Ageing:

decreased flexibility in skin, joint, vessel wall

Crosslinked tropocollagen

Biochemistry: Amino acids

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Degradation products

Wound healin,

rheumathoid arthritis, tumor metastasis

Collagenases

Procollagenases

Plasmin Metalloproteinase

„Clostridium hystolyticum”

(gas-gangrene)

Degradation of collagens

Collagens

Biochemistry: Amino acids

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Intracellular degradation of proteins

Blood plasma glycoproteins and intracellular proteins are degraded in lysosomes.

Half-life of proteins: 30 minutes-150 hours Receptor-mediated endocitosis (for antigen-antibody

complexes, LDL, Vitamin B

, protein hormones, insulin, viruses, toxins, ets.)

ATP-dependent protein degradation (for abnormal-damaged proteins)

Biochemistry: Amino acids

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Degradation of asialoglycoproteins

Sia Gal GA

Carbohydrate Protein

Endothelial cell

Sialilase

Gal – GA – Carbohydrate -Protein

Biochemistry: Amino acids

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Asialoglycoprotein-receptor

Liver

Gal Y

Protein

Lysosome

Amino acids

CH

– C – NH

R

O COOH OH OH

O

Gal: galactose

GA: N-acetylglucosamine Sia: sialic acid

Y

Biochemistry: Amino acids

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Ubiquitin (UB)

Enzymes (controlling metabolism) with short life-time

Abnormal proteins (mistakes in synthesis) Damaged proteins (denatured, oxidized, partially proteolyzed

Biochemistry: Amino acids

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Lys NH

N

Ubiquitin Mr = 8500

Gly – C - OH O

ATP

AMP

E

- SH E

- SH

E

- SH

UB – C – S _Enzim

(protein)

UB Gly – C - NH – Lys

O Isopeptide bond

Amino acids Degradation

protein

protein

O

Biochemistry: Amino acids

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Amino acid transport (γ – Glutamyl Cycle)

2

R H

γ-Glutamyl transpeptidase (transferase)

Cell membrane Glutatione (GSH)

HOOC - C - CH₂- CH₂ - C- N - C - C- N -CH₂- COOH

NH₂ O H O

(Glu) (Cys) ( Gly)

H H CH₂ H

cytosol

SH

Cys -Gly

Peptidase

COOH H - C – NH₂

CH₂ CH₂ C = O

N – H H- C – R COOH

Gly

Cys

COOH C – NH₂ R H

Oxoproline

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 39 ADP

Pi

GSH- synthetase

Genetic defect

ATP Gly

γ-Glutamyl- cysteine

Glu

γ-Glutamyl- cystein- synthetase

Genetic

defect Cys

ADP Pi

ATP

GSH *

COOH H - C – NH₂

CH₂ CH₂ C = O

N – H H- C – R COOH

•

hemolytic anemia

Biochemistry: Amino acids

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H C C

O COOH N

H

5 - Oxoproline 5 - Oxoprolinase

ADP

Pi ATP

Glutamyl- cyclotransferase

Biochemistry: Amino acids

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Glutathion

Glu

Cys ADP Pi

ATP

Glu - Cys

Gly ADP Pi

ATP (GSH) reduced

Glu – Cys - Gly Glutamyl-

cysteine synthase Glutathione synthase

SH

R – O - OH

Glutathion peroxidase

R –OH

H²O

NADPH

>500 Glutathion reductase

Biochemistry: Amino acids

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~1 Glu – Cys - Gly

Glu – Cys - Gly s

s

(GSSG) oxidized

GSH-GSSG

„redox buffer”

Detoxication:

-hydrogen peroxide and organic peroxide („frightful” secondery product of life)

Biochemistry: Amino acids

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Glutathione peroxidase (E-Se)

The enzyme contains a covalently bound selenium atom (Se);

its active site is a Cys analog, where S is replaced by Se

R O OH R OH H

E Se

selenolate H

GSSG

GSH

E Se SG

selenosulfide H

O

GSH

E Se OH selenic acid

SeH CH₂ O N C C H H

E

═

Biochemistry: Amino acids

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Amino acid metabolism: synthesis of nonessential amino acids, degradation/transformation of amino acids

„General reactions”:

1. Glutamate dehydrogenase

2. Aminotransferases (transaminases) 3. One-carbon transfer:

Tetrahydrofolate (THF) S-adenosylmethionine

Biochemistry: Amino acids

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Glutamate dehydrogenase

COOH C O CH

CH

COOH

=

α-keto glutarate

NH

H

O

Glutamate

dehydrogenase NADPH

COOH C NH

CH

CH

COOH H

Glu

Biochemistry: Amino acids

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Aminotransferases (transaminase)

Amino acid- ¹

H – C - COOH NH

R

α-ketoacid- ²

+ _{C - COOH}

O R

=

Amino acid- ²

H – C - COOH NH

R

α-ketoacid- ¹

C - COOH O

R

= +

Biochemistry: Amino acids

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Aminotransferases, (AT) contain pyridoxal phosphate (PP), a derivative of pyridoxine (vitamin B

), which forms Schiff-base intermediate

In native enzyme without substrate

Lys (CH₂)₄

N C H P

═

Schiff base

H – C - COOH NH₂ R¹ H – C - COOH

NH₂ R²

=

H – C - COOH N

C H P

R¹

═ Aldimine

Biochemistry: Amino acids

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α-ketoacid

C - COOH O

R¹

=

C - COOH O

R²

= NH₂

CH₂ P

C - COOH N

R¹

=

CH₂ P H₂O

H₂O Ketimine

α-ketoacid

Pyridoxamine phosphate

H⁺

Sum: AA₁+ α-keto A₂ AA₂ +α-keto A₁

Biochemistry: Amino acids

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Aminotransferases in Hospitals

SGPT glutamate + pyruvate alanine + α – ketoglutarate glutamate – pyruvate transaminase

ALAT (alanin – aminotransferase)

sGOT glutamate + oxalacetate α – ketoglutarate + aspartate glutamate – oxaloacetate transaminase

ASAT (aspartate – aminotransferase) LDH lactate dehydrogenases

GLDH glutamate dehydrogenase

In myocardial infarction: sGOT peak at 20 hs, LDH

toxic liver damage: sGOT peak at <12 hs, LDH

Exempt from ammonia and substitute for essential amino acid

Biochemistry: Amino acids

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One-carbon transfer:

H

N N N

OH N

H H

H

H CH

H

C – N –C – CH

H H

Pteridine

O

p-Amino

benzoate Glutamate

(THF) Tetrahydrofolate

5

10

Biochemistry: Amino acids

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N H

S N R H O

O

═

Sulfonamide

(antibiotic)

Biochemistry: Amino acids

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CH

CH

CHO CHNH CH CO

Most reduced Most oxidized

═

Methyl Methylene Formyl Formimino Methenyl carried by

carried also by

S-adenosyl-Met (more efficient)

They are interconvertable, serving as donors as well as acceptor

biotin N

C

C N

Tetrahydrofolate

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 53

S-adenozyl-methionine

COOH C – NH

CH

CH

S

H

H

C CH

H

OH OH

H O

NH

N H

N N H

N

Ribose (R)

Adenin (A) Methionine

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 54

COOH C – NH₂ CH₂

CH₂ H

H₃C S⁺ C⁵R A

Methionine-adenosyl - transferase ATP

Pi Pi PPi

Pi

S-Adenosyl homocystein - methyl transferase

CH₃

Acceptors

S-Adenosyl methionine

Activated-methyl cycle

Biochemistry: Amino acids

2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006

Met

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 55

COOH C – NH₂ CH₂

CH₂ H

S

COOH C – NH₂

CH₂ CH₂ H

CH₃

S

COOH C – NH₂

CH₂ CH₂ H

SH

Activated-methyl cycle

Met

CH₃

N⁵– methyl – THF Homocysteine -

methyltransferase (Vit B₁₂)

H₂O

Adenosyl

Homocysteine

diet

Adenosyl S-Adenosyl-homocysteine

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 56

Homocysteine and atherosclerosis Diet

Met (1-2 g/day)

S-adenosyl-Met

Met

Homo-Cys

S – A - Homocys

- ^CH

THF ^Ser

Homo Cys:

Thrombosis

5-methyl- THF

Biochemistry: Amino acids

2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006

Cystatione synthase B₆

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 57

Ser Gly

NADPH

Homo-Cys in blood: 80% protein disulfide

≈

18% Homocys-Cys with Homocys-Homocys

≈

2% Free Homocys

Deficiency male > female

Cystatione synthase B

Cystatione

Cys

d

c

d

c

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 58

Biosynthesis of nonessential amino acids

Glucose

3 – Phosphoglycerate

Pyruvate

Ac – CoA

Tyr Phe* Ser

Cys

Ala

Glu

Met*

Gly

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 59

Asp Oxalo- Citrate

acetate

Gln Glu

α-keto- glutarate Succinyl-

CoA

Citric cycle Asn

Glu Gln

Arg Pro

Glu: „central role”

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 60

Biosynthesis of Cys

Met

HOOC – C – CH₂– CH₂– SH NH₂

Homocysteine

Homocystin -

uria Cystathionine*

synthase (PP)

H₂O

HOOC – C – CH₂– CH₂– S – CH₂ – C – COOH H H

NH2 NH₂

HO – CH₂– C – COOH H

NH₂

Ser

H

Biochemistry: Amino acids

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Cystathione

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 61 Cystathionine

H

Cystathionuria

O α- ketobutyrate

═

HS – CH₂– C – COOH NH₂

Cys

*

In Synthase defect homocystein is accumulated in blood :

thrombomodulin in urine: homocystin NH⁺⁴ H2O

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 62

Biosynthesis of tyrosine

COOH C CH

H NH

Phe*

O

H

O

THB DHB

COOH C = O CH

Aminotransferase

Phenylpyruvate

Phenyllactate Phenylacetate

Phenylalanine- hydroxylase

Phenylketonuria (PKU):

Dg: Mental retardation (high Phe level inhibits serotonin biosynthesis) In mental hospital: 1% of patients PKU Dg: Phe in the blood

DNS test for phenylalanine- hydroxylase

Th: exempt from protein(diet) and addition of amino acids free from Phe

IQ ~93 ( ha diéta 1 év után IQ~53)

Biochemistry: Amino acids

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DHB: dihydrobiopterine

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 63

Amino acid degradation

Protein

amino acid Catabolism

25%

75%

There is no amino acid pool (in contrast with lipids and glucose):

They may serve as energy sourse

From α-amino groups urea is synthesized (ornithine cycle).

Carbon skeleton enters citric acid cycle.

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 64

Fate of nitrogen

N in urine (%): Urea 86 Creatine 4.5 Ammonia 2.8 Urate 1.7 Others 5

In liver:

amino acid α-keto-glutarate NADH NH

Ser Thr Oxidative

deamination

α-ketoacid Glu NAD

Aminotransferase Glutamate

dehydrogenase

Intestinal bacteria

Gln

Aminotransfer Urea

NH

(normal level in blood 25-40 μM) extremely toxic for central nervous system

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 65

Ammonia elimination (Ornithine- cycle)

NH

+ CO

+ 3ATP + H

O + Asp Urea + 2ADP + 2Pi + AMP + PPi + Fumarate

NH

H

O

CO

2ATP

2ADP Pi

O O

O¯

═

Carbamoyl - P

Transfer

anhydride bond (high transfer potential)

Carbamoyl – phosphate synthetase

+ Carbamoyl – P used for pyrimidine synthesis is produced by a slightly different mechanism

Ornithine

Free (from intestive))

O ¯ P O C NH2

═

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 66

COOH C – NH₂ (CH₂)₃

N – H

C NH₂ H

O

═

COOH C – NH₂ (CH₂)₃

N H₂

COOH C–NH₂ CH₂

COOH H

Mithochondria

Asp Citruline

Ornithine

Ornithine – transcarbamoylase

Arginino succinate synthetase ATP

AMP PPi

Pi Pi Condensation

Ornithine cycle

Hydrolysis

Arginase

NH₂

C== O NH₂

Urea

H₂O

Cytosol

Carbamoyl – P

H

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 67

COOH C – NH₂ (CH₂)₃

N – H NH₂ H

HN - C-

═

COOH C – NH₂ (CH₂)₃

N – H C N H

HN H Arginino –

succinase (liáz)

Argininosuccinate

H C COOH HOOC C H

═

Fumarate Protein synthesis

COOH C – H CH₂

COOH

Biochemistry: Amino acids

2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006

═

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 68

Gln

Glu

α-ketoglutarate

Gln-áz ATP

HN

Gln szintetáz

Gln-

syntetase Gln-ase

N-acetil-Glu

Ac-CoA

Intestine NH

(≈ 40%)

Glu-dehyd- rogenase

(20%) ⊕

⊕

Control of ornithine cycle

Biochemistry: Amino acids

2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006

Carbamoyl-phosphate synthetase

Ornitine cycle

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 69 Carbamoyl-

phosphatase synthetase

2ATP CO

P - C - NH

O

Ornithine cycle Urea

Carbamoyl – P - synthase

Liver - blood

Biochemistry: Amino acids

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Fate of carbon skeleton in amino acid degradation

Amino acids, after deamination, may lead to glucose or ketone body formation;

amino acids as energy sources:

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 71

Ketogenic and glucogenic amino acids

Glucose PEP Pyruvate

Acetyl-CoA Acetoacetate Ketone bodies Oxaloacetate

Malate α-ketoglutarát

Fumarate

Succinyl-CoA Methylmalonyl-CoA

Gly Ser

T

rp

Ala Cys S

O

Ile Leu Lys

T

rp

yr

Phe

Glu Gln

His

Pro

Arg

Val

Met Thr

Asp Asn

T

yr

Biochemistry: Amino acids

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Catabolism of Phe and Tyr (both ketogenic and glucogenic)

COOH C CH2

H NH²

COOH C CH2

H NH²

O2 Phenylalanine H2O hydroxilase

(monooxygenase)

Phenylketonuria (PKU) hyperphenilalaninemia I

Tyr

Melanine

Epinephrine

Thyroxine

Tyrosinemia type II

Phe

Biochemistry: Amino acids

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Dihydropteridine reductase OH

THB, DHB

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 73

Phenylketonuria (PKU)

Phe Tyr DOPA

O

Phe- O

hydroxylase Tyr-

hydroxylase

Melanine

THB DHB

NADH

DHB-reductase

„kofaktor”

X

Norepinephrine

Epinephrine

„classic”

THB

Tyr-

aminotransferase

Biochemistry: Amino acids

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Homogentisate

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 74

Homogentisate

Fumarate Acetoacetate

Y

Tyrosinemia (eye and skin lesion)

X

Y Alcaptonuria.

homo-

gentisate in urine „pigment arthritis”

(Ochronosis) Homogentisate-

oxidase

Biochemistry: Amino acids

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THB: tetrahydrobiopterin (BH4)

(„cofactor” - PKU)

THB DHB

Trp O

CO

Serotonin

Trp-hydroxylase

Arg

NO

THB DHB

Citrulline PKU: Phenylketonuria

THB DHB

DHB-reduktáz Tyr DOPA

Tyr-

hydroxylase

NO-synthase

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 76

COOH

C CH

H NH

Serotonin synthesis

N H

Trp

THB DHB

O

Tryptophane hydroxylase

(in brain)

Biochemistry: Amino acids

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Hydroxytriptophane

Decarboxylase (Vitamin B

)

CO

N

-

CH

–CH

NH

(5-Hydroxytryptamine)

Serotonin

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 77

5 – Hydroxyindole acetate

N H

HO- -

CH

-COOH

Mono amine oxidase

NH

(MAO) O

Inhibitors

Serotinin

Degradation of serotonin

Biochemistry: Amino acids

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 78

Neutrotransmitter:

LSD competition (hallucination),

Control of temperature, sleep, mood etc.

Vasoconstriction

Growth hormon secretion

60% of Try (normally 1%) is converted to Serotonin.

Decreased NAD production (pellagra symptoma)

Serotonin actions

Intestinal carcinoma: Argentaffinoma Serotonin

Biochemistry: Amino acids

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Catabolism of Ile ^(both ketogenic and glucogenic)

COOH C – NH2

C – CH

CH

CH

H H

COOH C = O

C –

CH2

CH

Isoleucine transaminase α-keto Glu Glu

C –S - CoA C – CH3

CH

CH3

H

HS-CoA CO

NAD NADH

Ketoisocaproate dehydrogenase α-keto

isocaproate Isovaleryl-CoA

Ile

Biochemistry: Amino acids

2011.09.13.. TÁMOP – 4.1.2-08/2/A/KMR-2009-0006

degradation

TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 80 C –S - CoA

C – CH3

C =

H O

=

C –S - CoA C – CH3

C -

H

O =

C – CH3

CH CH3

H O =

H

FADH

Isovaleryl-CoA dehydrogenase

Dehydrogenase

NADH NAD

H

O

Hydratase

=

Methylcrotonyl-CoA

FAD Isovaleryl-CoA

Biochemistry: Amino acids

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TÁMOP – 4.1.2-08/2/A/KMR-2009-0006 81

HS -CoA

CH₃– C – S – CoA

Acetyl-CoA

CH

CH

C = O S - CoA

COOH C – CH₃

C = O S -CoA H

CO

ATP

Carboxylase (Biotin)

Thr

Met Val

O=

Biochemistry: Amino acids

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Propionyl-CoA Methyl-malonyl-CoA

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Cobalamin (Vitamin B12)

Coenzyme B12 catalyzes intramolecular rearrangement *:

H COOH H - C - C – H

H

C – S – CoA O

H COOH H - C - C – H

H C – S – CoA

O

Methylmalonyl CoA mutase

Coenzyme B12

Methylmalonyl CoA Succinyl-CoA

Citrate cycle ^Ser

THF

Porphyrins Gly

*

Heme

Biochemistry: Amino acids

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