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Flashcards in Protein and AA metabolism Deck (26):
1

Hartnup Disease

Defects in AA reabsorption -> Cystinuria

2

Exopeptidase

attacks at C terminus or N terminus ends

3

Endopeptidase

Attacks within the protein at a specific site

4

Intracellular proteolytic control

via large proteasome that cleave polyubiquinated proteins.

5

Extracellular proteolytic control

Proteolytic enzymes secreted as needed. First secreted as inactive zymogens, that are activated by proteolytic cleavage -> ex. inactive trypsinogen and chymotrypsinogen are released into the SI lumen. Trypsinogen is activated by enterokinase and then activated trypsin activates chymotrypsinogen into chymotrypsin.

6

Essential AA

TIM HRKL VFWQ

7

Ketogenic AA

Leu and Lys

8

Ketogenic and Glucogenic

Ile, Trp, Phe, Tyr, Thr

9

Glucogenic AA

His, Met, Gly, Val, Arg, Ala, Pro, Asn, Asp, Ser, Gln, Glu, and Cys

10

Common precursors of AA

OAA -> D
Pyruvate -> A, V, L
Ribose 5 P -> H
3 -PG -> S
å KG -> E
PEP + Erythrose 4P -> F

11

AA that can enter TCA cycle and where?

F, Y, D -> Fumarate
M, V, T, I -> Propionyl CoA -> Succinyl-CoA
Q, P, H, R -> E -> å ketoglutarate

12

Function of transaminases and cofactor

transfer amino group from AA to an å-ketoacid and require pyridoxyl 5-P (B6)

13

Removal of amino group from Glutamate generates å -KG via 3 mechanisms

1.) oxidation deamination by glutamate dehydrogenase which releases ammonium ion
2.) transfer of Amino group to pyruvate by ALT
3.) transfer of amino group to OAA by AST

14

Homocystinuria

Deficiency in cystathione B-synthase leads to buildup of homocysteine, which can accumulate and be excreted in urine.

15

Where are BCAs degraded?

BCAs are not degraded in liver due to the absence of the required aminotransferase. Instead they are degraded mainly in muscle, kidney, and brain.

16

Consequences of hyperhomocysteinemia and homocystinuria

Vitamin deficiencies of (B6, B12, and folic acid) or genetic defects in the enzyme cystathionine ß-synthase cause defective metabolism of homocysteine and can lead to heart disease and stroke, mental retardation.

17

Maple syrup urine disease

AR disease resulting from deficient branched-chain å-keto acid dehydrogenase complex (BCKD). BCAs present in urine, which give hallmark of maple syrup smell. Higher in mennonite, amish, and jewish populations.

18

Phenylketonuria (PKU)

deficiency in phenylalanine hydroxylase. Phe instead is converted to phenyllactate and phenylacetate, resulting in severe impairment of brain function.

19

Trp derivatives
Ser derivatives
Tyr derivatives
Glu derivatives

Trp: serotonin -> melatonin and Niacin -> NAD
Ser: Acetlycholine
Tyr: Dopamine -> Norepi -> Epi., Thyroid hormones, Melanin
Glu: GABA

20

Albinism and Tyrosinase

Albinism is due to lack of melanin. Conversion of tyrosine to melanin is via tyrosinase. Blocking of this enzyme results in partial or complete absence of pigmentation in skin.

21

Thyroglobulin and Thyroid hormones

Thyroglobulin is made from thyroid and has over 120 tyrosine residues.

22

Ammonia removal in brain vs ammonia removal in other tissues

Glu -> Gln in brain and then Gln -> Glu in liver and NH4+ enters urea cycle
Ala -> pyruvate with å KG -> Glu and NH4+ enters urea

23

Hyperammonemia w/ Orotic aciduria

X-linked recessive defect of ornithine transcarbamoylase.

24

Ammonia toxicity

excessive ammonia due to disorders in the urea cycle or liver failure can have highly toxic effects on the brain and CNS.

25

Urea cycle and the high protein diet

urea production is increased by a high protein diet and decreased by high carb diet.

26

Creatine is made from which 3 AA?

R, G, M