Flashcards in Protein and AA Metabolism Deck (26):
Essential Amino Acids
W, F, M
R, H, K
L, I, V
Become acetyl - CoA or acetoacetate
Glucogenic and Ketogenic AAs
I, W, F, Y, T
Can become ketogenic or glucogenic (pyruvate or TCA intermediates --> GNG)
AAs that are metabolized to a-ketoglutarate
Q, R, H, P ----> E ----> a-KG
AAs that are metabolized to succinyl-CoA
T, M, I, V ----> propionyl CoA ----> succinyl CoA
AAs that are metabolized to fumarate
F, Y, D
AAs that are metabolized to OAA
ALT (alanine aminotransferase)
Catalyzes pyruvate + glutamate ---> alanine + a-KG
AST (aspartate aminotransferase)
Catalyzes OAA + glutamate ---> aspartate + a-KG
GA (glutamate aminohydrolase)
Catalyzes glutamine + H2O ---> glutamate + NH3
Coenzyme PLP (pyridoxyl-5'-phosphate) a derivative of Vit B6.
Cause of Homocsytinuria
Cystathione b-synthase does not work, causing build up of Homocysteine (in the Met pathway). Requires PLP as a coenzyme.
Cystathione b-synthase is defective or a Vit B6 deficiency can cause it.
Most affected systems include the eye, skeletal, CNS, and vascular system.
L, I, V
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.
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.
Trp (W) derivatives (2)
1. serotonin ---> melatonin
2. niacin ---> NAD(P)+
Ser (S) derivative (1)
Tyr (Y) derivatives (3)
1. Dopamine ---> Norepi ---> Epi
2. Thyroid hormones
Glu (E) derivative (1)
Lack of melanin. Tyr to melanin conversion is blocked due to defect of tyrosinase.
Removing N from brain
Brain: removed as a-KG --> E then E ---> Q then to liver Q ---> E (ammonia released to urea cycle).
Removing N from muscle
A from muscle to blood to liver. A ---> E to the urea cycle (regenerate a-KG).
Used quickly to generate ATP. Stored in muscle, brain and sperm.