Special Products of Amino Acid Metabolism

Question 1

S-adenosyl methionine (SAM)

Answer 1

synthesized from methionine and ATP via methionine adenosyl transferase
rxns requiring transfer of a methyl group

Question 2

NAD

Answer 2

nicotinate mono nucleotide product of tryptophan metabolism
quinolinate substrate for quinolinate phosphoribosyl transferase which forms nicotinate mono nucleotide which is then converted to NAD

Question 3

Carnitine

Answer 3

derived from epsilon-N-trimethyllysine which is formed by methylation of lysyl residues is protein
requires SAM
trimethyllysine converted to Carnitine by enzymatic steps requiring Fe, alpha ketoglutarate, and O2
transports fatty acids across the mitochondrial membrane

Question 4

Coenzyme A

Answer 4

from pantothenic acid requiring cysteine

Question 5

Catecholamines (epinephrine and norepinephrine)

Answer 5

derived from tyrosine

synthesized in the adrenal medulla where they are stored and released into the general circulation when required

Question 6

Acetylcholine

Answer 6

derived from serene
3 methyl groups from SAM
choline acetyl transferase catalyzed formation from choline and acetyl CoA

Question 7

Gamma-aminobutyric acid (GABA)

Answer 7

formed by glutamate decarboxylase

Question 8

Serotonin

Answer 8

formed from tryptophan by tryptophan hydroxylase (requiring tetrabiopterin) and aromatic amino acid decaroxylase (requiring pyridoxal phosphate)
neurotransmitter, vasoconstrictor, and stimulator of smooth muscle contraction

Question 9

Melatonin

Answer 9

add acetyl and methyl group to serotonin (from tryptophan)
produced in pineal gland
may be involved in light/dark cycles, seasonal circadian rhythms

Question 10

Nitric oxide

Answer 10

synthesized by nitric oxide synthase from arginine
made in neurons, macrophages, blood vessel endothelial cells
requires O2, NADPH, tetrahydrobiopterin, FMN, FAD, and (FeIII) heme
3 isozomes= iNOS in macrophages (inducible), nNOS, and eNOS stimulated by Ca and calmodulin

Question 11

Creatine

Answer 11

from glycine and arginine and methylation from SAM
serves as a reservoir of high energy phosphate primarily in muscle
formed nonenzymatically from creatine phosphate and is entirely secreted in the urine

Question 12

Glutathione (gamma- glutamylcysteinylglycine)

Answer 12

synthesized from its three constituent amino acids by rxns involving activation of the carboxyl groups with ATP
2 ATP for every GSH
nontoxic reservoir of reducing power. and present in high concentrations

Question 13

Polyamines

Answer 13

(putrescine, spermidine, and spermine)
derived from ornithine and methionine
role in cell division

Question 14

Melanin

Answer 14

tyrosine is the source

tyrosinase oxidizes tyrosine resulting in dopa quinone which is a precursor to melanin

Question 15

What is the cause of classical alalbinism?

Answer 15

deficiency of tyrosinase

Question 16

Histamine

Answer 16

decarboxylation of histamine by aromatic amino acid decarboxylase
vasodilator and hormone

Question 17

Choline and ehtanolamine

Answer 17

decarboxylation products of serine

incorporated into phosphatidyl choline and phosphatidyl ethanol amine and phosphatidyl serine

Question 18

What is a precursor of all of the sphigolipids?

Answer 18

serine

Question 19

Purine biosynthesis requires which amino acids?

Answer 19

glycine, glutamine, and aspartate

Question 20

Pyrimidine biosynthesis requires which amino acids?

Answer 20

aspartate and glutamine

Question 21

What is required for the synthesis of porphyrins?

Answer 21

glycine