Protein Metabolism III: Sulfer and Aromatic Amino Acid Flashcards Preview

Dems Unit 2 Part 2 YAAAY > Protein Metabolism III: Sulfer and Aromatic Amino Acid > Flashcards

Flashcards in Protein Metabolism III: Sulfer and Aromatic Amino Acid Deck (24):
1

sulful containing AA

cysteine (unessential)
methionine (essential

2

cysteine function

structural integrity of proteins (esp extracellular)

important role in redox potential
glutathione: tripeptide that controls redox potential via reversible reaction
Gsh--> Gssg

3

Methionine

produces intermediate in cysteine production: SAM

4

SAM

major carbon donor & high energy storage unit like ATP

5

Recycling MET rxn

MET>SAM>SAH>Homocysteine>Met
MET>SAM>SAH>Homocysteine>Crystathione>Cysteine

*Homocystein>Met requires THF and Vitamin B12 to transfer back CH3 group
*Homocysteine>Crystathione enzyme defective in homocystinuria, enzyme also requires B6

6

hyperhomocystemia

cause: low folate, B6, B12, vascular disease

Description: CV disease

AA: Cysteine becomes essential

Treat: Folate, B6, B12

7

homocystinuria

cause: defective CBS: can't convert homocysteine>cysteine

description: mental retardation, osteoporosis, lens subluxation, tall with kyphosis, vascular disease, thrombosis, atherosclerosis (MI & Stroke)

AA: cysteine becomes essential

Treat: supplement B6 to force CBS activity

8

cysteinuria

cause: hereditary deficit of renal PCT and intestinal AA transporters for COLA (cysteine, ornithine, lysine, arginine)

Description: kidney stones/ failure

Diagnose: urinary cyanide nitroprusside test

Treat: Urinary alkinization (potassium citrate, acetazolamide); chelating agents

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CBS enzyme

requires B6

10

reaction homocysteine> met

requires THF, vitamin B12

11

THF overview

¬ Synthesized in bacteria
¬ Precursor to folate
¬ One carbon group in any oxidative state is bonded to N-5 or N-10

12

THF Forms

Most reduced Form: methyl group
Oxidized Form: methylene group
Most Oxidized Form: methenyl, formyl, formin, or no group

Inter-convertable forms used to donate carbon in many reactions

13

GSH overview

¬ Redox Buffer
¬ Highly soluble tripeptide as opposed to Cys
¬ Milimolar in some tissues

14

GSH Functions

Thiol redox buffer = SH buffer; proteins in reduced form/ regulate activity

Enzyme cofactor for Gst (glutathione transferase)

Reduce Hydrogen peroxide to water; H202 H20; protects against ROS

15

Metabolism Products of tryptophan, phenylalanine, tyrosine

tryptophan: pyruvate or acetoacetate

Phenylalanine & tyrosine: fumerate or acetoacetate

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Tryptophan Rxn

Tryptophan Hydroxylase: cofactor BH4
Trp>>>> serotonin (NT); melatonin (hormone); niacin (energy)

17

Phenylalanine Rxn

Phenylalanine hydroxylase: Cofactor BH4, deficient in PKU
Phe > Tyr

18

Tyrosine Rxn

Tyrosine hydroxylase: cofactor BH4
Tyr>Dopa>>> Catecholamines (dopamine, NE, epinephrine)

19

PKU

Cause: deficient Phe hydroxylase or BH4 cofactor (malignant)

Description: excessive Phe leads to excess phenylketones in urine; Intellectual disability, growth retardation, fair skin, eczema, musty body odor

AA: tyrosine becomes essential

Screen: 2-3 days after birth/ after mom's enzyme gone

Treat: decrease dietary Phe and increase tyrosine; avoid aspartame which contains Phe

20

maternal PKU

lack of proper therapy during pregnancy

Infant: microcephaly, intellectual disability, growth retardation, congenital heart defects

21

Akaptonuria

cause: deficient homogentisate oxidase in tyrosine degradation pathway to fumate

Description: dark connective tissue, brown pigmented scalar, urine black with exposure to air; debilitating arthralgia because homogentisic acid is toxic to cartilage

Treatment: low Phe diet with tyrosine

22

Albinism

cause: defect in Tyrosine metabolism and therefore deficiency in melanin production

Complete albinism: deficit tyrosinase

description: decreased pigmentation of eyes, hair, skin

23

Parkinson's

dopamine is reduced in parkinson's
one treatment is l-dopa which is dopamine precursor

24

MAOIs

MAO breaks down products of dopamine, NE, epinephrine, serotonin

hypertensive crisis with tyramine rich foods like cheese