Protein and AA Metabolism

Question 1

Essential Amino Acids

Answer 1

W, F, M
R, H, K
L, I, V
T

Question 2

Ketogenic AAs

Answer 2

L, K

Become acetyl - CoA or acetoacetate

Question 3

Glucogenic and Ketogenic AAs

Answer 3

I, W, F, Y, T

Can become ketogenic or glucogenic (pyruvate or TCA intermediates –> GNG)

Question 4

AAs that are metabolized to a-ketoglutarate

Answer 4

Q, R, H, P —-> E —-> a-KG

Question 5

AAs that are metabolized to succinyl-CoA

Answer 5

T, M, I, V —-> propionyl CoA —-> succinyl CoA

Question 6

AAs that are metabolized to fumarate

Answer 6

F, Y, D

Question 7

AAs that are metabolized to OAA

Answer 7

N, D

Question 8

ALT (alanine aminotransferase)

Answer 8

Catalyzes pyruvate + glutamate —> alanine + a-KG

Question 9

AST (aspartate aminotransferase)

Answer 9

Catalyzes OAA + glutamate —> aspartate + a-KG

Question 10

GA (glutamate aminohydrolase)

Answer 10

Catalyzes glutamine + H2O —> glutamate + NH3

Question 11

Transaminases require:

Answer 11

Coenzyme PLP (pyridoxyl-5’-phosphate) a derivative of Vit B6.

Question 12

Cause of Homocsytinuria

Answer 12

Cystathione b-synthase does not work, causing build up of Homocysteine (in the Met pathway). Requires PLP as a coenzyme.

Question 13

Homocystinuria

Answer 13

Cystathione b-synthase is defective or a Vit B6 deficiency can cause it.
Most affected systems include the eye, skeletal, CNS, and vascular system.

Question 14

BCAAs (3)

Answer 14

L, I, V

Question 15

MSUD

Answer 15

Deficient in BCKD, so the pt cannot breakdown BCAAs.
Causes maple syrup smell of urine. Can cause blood accumulation causing toxic affects on brain function and eventually mental retardation.
Diet must limit BCAAs, and can be restored with thiamine supplements in mild forms.

Question 16

PKU

Answer 16

Defect in phenylalanine hydroxylase (PAH). Phe cannot be broken down to Tyr and subsequent protein, catecholamine, thyroxine or melanin synthesis cannot happen.
Phe insteade converted to phenylpyruvate then to phenyllactate and phenylacetone (causes the smell).
Can cause neurotransmission problems and impair brain function.

Question 17

Trp (W) derivatives (2)

Answer 17

1. serotonin —> melatonin

2. niacin —> NAD(P)+

Question 18

Ser (S) derivative (1)

Answer 18

1. ACh

Question 19

Tyr (Y) derivatives (3)

Answer 19

1. Dopamine —> Norepi —> Epi
2. Thyroid hormones
3. Melanin

Question 20

Glu (E) derivative (1)

Answer 20

1. GABA

Question 21

Albanism

Answer 21

Lack of melanin. Tyr to melanin conversion is blocked due to defect of tyrosinase.

Question 22

Removing N from brain

Answer 22

Brain: removed as a-KG –> E then E —> Q then to liver Q —> E (ammonia released to urea cycle).

Question 23

Removing N from muscle

Answer 23

A from muscle to blood to liver. A —> E to the urea cycle (regenerate a-KG).

Question 24

Urea Cycle

Answer 24

Draw cycle

Question 25

Phsosphocreatine

Answer 25

Used quickly to generate ATP. Stored in muscle, brain and sperm.

Question 26

Creatine

Answer 26

Made of R, G, M

Used to diagnose kidney dysfunction and muscle degeneration.