Amino Acid Metabolism

(Voet & Voet Chapter 16)

Deamination :

1). The amino group is transferred to \-ketoglutarate by transaminase (PLP/PMP) to form glutamate, and then diaminated in the mitochondrion to yield NH4+ by glutamate DHase.

2). Nitrogen is transported to liver either by glucose-alanine cycle or glutamine.

Urea Cycle : 3). The ammonotelic, ureotelic, and uricotelic organisms excrete NH4+, urea, and uric acid, respectively.

4). Urea is only synthesized in the liver by urea cycle enzymes (mito & cytosol).

5). Mitochondrial CPS I is the rate-limiting step of urea cycle and is allosterically activated by N-acetylglutamate.

6). How many free energy is required and produced per urea cycle?

7). What is the possible metabolic effects of hyperammonemia in the brain?

Catabolism of the Carbon Skeletons : 8). What kind of metabolic intermediates are produced by the carbon skeletons of glucogenic and ketogenic amino acids, respectively?

9). Which cofactor is required for the hydroxylation of aromatic amino acids (Phe, Tyr, Trp)? Is the cofactor a vitamin? How is it synthesized? (Error in p. 747).

Biosynthesis Biological Active Compounds : 10). ALA, which is synthesized from glycine and succinyl-CoA, is converted to PBG for biosynthesis of heme.

11). Epinephrine, norepinephrine, dopamine, serotonine, GABA, and histamine are hormones and/or neurotransmitters derived from amino acids. How?

12). What kind of compounds provide C1 unit for biosynthesis?

Biosynthesis and Nitrogen Fixation : 13). What is the difference between essential and nonessential amino acids?

14). Nitrogen is only fixed by nitrogenase (Fe- and MoFe- proteins) to form NH3 in the nitrogen-fixing bacteria, diazatrophs. What is the energy reqirements?

Practice Problem : Question 2, 5, and 10, Chapter 24 (Voet & Voet p.784)

Additional Information :

fଧg  (Phenylketonuria, PKU; Tetrahydrobiopterin Deficiency)
iħg  (Homocystinuria)

ߧf]Maple Syrup Urine Diseas, MSUD^

Last modified on 2000.12.21 by K.-J. Hsiao (s)                                      [ ]