Nitrogen, AAs, and Ntides Flashcards Preview

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Flashcards in Nitrogen, AAs, and Ntides Deck (47)
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1

Role of Aminotransferases

Transfer NH3 from AA to alpha-ketoglutarate to turn it into glutamate (and AA become alpha-keto acid)

2

Aspartate Aminotransferase

Unique aminotransferase that transfers NH3 from glutamate to OAA, forming aspartate and alpha-ketoglutarate

3

Aspartate Aminotransferase Cofactor

Vitamin B6 Pyridoxal Phosphate transfers amine in pyridoxamine phosphate form

4

Oxidative Deamination

Glutamate Dehydrogenase catalyzes glutamate conversion to alpha-ketoglutarate w/ release of free NH3

5

Ammonia Transport and Release to/in Liver (3)

Glutamine synthetase adds free NH3 to glutamate in most tissues to create glutamine
Glutamine carries it through blood to liver
Glutaminase and glutamate dehydrogenase remove the two amines in that order to yield glutamate then alpha-ketoglutarate

6

Urea Production Cycle (5 long)

Carbamoyl phosphate synthetase I adds CO2 and NH3 (first two sources of stuff for urea) to form carbamoyl phosphate
Carbamoyl phosphate adds to Ornithine to form Citrulline which can be transported out of mt matrix
Aspartate (source of urea's 2nd N) adds to Citrulline to form arginosuccinate
Fumarate leaves to form Arginine, which has guanidino group head
Guanidino group leaves and becomes urea, leaving ornithine which can be transported back into matrix

7

N-Acetylglutamate (formation and function)

Formed from Arginine-activated Acetyl CoA adding to glutamate
Required to activate carbamoyl phosphate synthetase I for urea production

8

Source of Ammonia in Urine

Glutamate dehydrogenase in kidneys

9

Hyperammonemia (cause, symptom, treatment)

When you have liver disease bc liver is making urea
High glutamine levels in blood
Phenylbutyrate converts into phenylacetate, which can combine w/ glutamine to form phenylacetylglutamine which will be excreted out

10

2 Exclusively Ketogenic AAs

Leu and lys

11

4 Gluco and Ketogenic AAs

Tyr, Ile, Phe, and Trp

12

Degradation of Asn and Asp

Asn converted to Asp converted to OAA (aspartate aminotransferase)

13

Pro, Arg, His, and Gln Degradation

Feed into glutamate can turn into alpha-ketoglutarate for glucogenic effects

14

Ala Degradation

Gives NH3 to alpha-ketoglut (becomes glutamate) to become pyruvate

15

Gly and Ser Degradation

Gly becomes ser via THF-producing rxn, and ser becomes dehydrogenated to pyruvate

16

Phe and Tyr Degradation (2)

Phenylalanine hydroxylase converts Phe to Tyr via Tetrahydrobiopterin putting -OH on phenyl ring
Tyr converted to fumarate and acetoacetate

17

Degradation of Leu, Val, and Ile (3 rxns and 2(3) products)

Transaminated to alphaketoacids
Oxidative decarboxylation to FAs
FAD-linked dehydrogenation
Leu is ketogenic, forms acetoacetate + acetyl CoA
Val and Ile are glucogenic, form succinyl CoA

18

Maple Syrup Urine Disease

Defect in alpha-ketoacid dehydrogenases breaking down the alpha-ketoacids formed from leu/val/ile degradation

19

Met Degradation

Generates SAM which is used as methyl donor for chromatin remodeling/DNA, then converted to Homocysteine which can be reconverted to Met + THF or Serine added to form Cysteine

20

Homocysteine Clinical Consideration

Higher levels correlate w/ cardiovascular problems

21

THF Use

AA and Purine Synth

22

Main Function of Tyr

Hormone Production

23

Dihydrobiopterin (BH2) Reductase Deficiency (action, and 3 clinical effects, and treatment note)

Can't reset BH2 to tetrahydrobiopterin (BH4), causing phenylketouria by messing up phenylalanine hydroxylase
also messes up tyr hydroxylase production of DOPA/CATs and
trp hydroxylase 5-HT production
Difficult to treat bc even if supplement w/ BH4 it can only be used once

24

3 Causes of Phenylketouria (most to least common)

Phenylalanine hydroxylase deficiency
Dihydrobiopterin Reductase Deficiency
GTP Cyclohydrolase Deficiency - can't produce BH2

25

2 Biochemical Effects of Phenylketouria (2.6)

Can't produce tyr from phe, so miss tyr products like melanin, CATs, and fumarate and acetoacetate
Excess phe converted to phenyl pyruvate and then have buildup of toxic organic acids

26

Major Clinical Effect of Untreated Phenylketouria

Progressive severe retardation

27

Albinism Cause

Melanin deficiency from enzyme deficiency to convert bw tyr and melanin

28

Homocystinuria

Cystathione Beta-Synthase Deficiency can't degrade homocysteine

29

Alkaptonuria

Homogentisic Acid Oxidase deficiency causes urine to turn black from oxidation

30

5 Donors to Purine Synth (& what they donate)

Glutamine - 2 Ns
Aspartate - 1 N
Glycine - Backbone of 2Cs and 1N
N-formyl-THF - 2Cs
CO2 - 1C