L31- Amino Acid Synthesis Flashcards
Which cofactor is required for the conversion of tyrosine to dopamine?
Tetrahydrobiopterin (THB)
Which enzyme catalyzes the conversion of 3,4-dihydroxyphenylalanine (Dopa) to dopamine?
Dopa decarboxylase.
How is thyroxine synthesized?
It is made from the iodination of two tyrosines residues on thyroglobulin.
Which pigment molecule in the skin and eyes is made from tyrosine?
Melanin.
Which enzyme deficiency results in albinism?
Tyrosinase deficiency.
What is the function of S-adenosyl methionine?
It transfers methyl groups.
Which coenzyme catalyzes the transfer of one-carbon fragments from formic acid to methyl groups?
Tetrahydrofolate (THF).
Which form of tetrahydrofolate (THF) is most effective for the transfer of one-carbon fragments?
The polyglutamyl form (the other form is the methyl derivative, which is the major form of THF in the blood).
From which vitamin is tetrahydrofolate derived?
Vitamin B9 (folic acid).
From which amino acids can one-carbon fragments be synthesized?
Glycine, serine, histidine and, to some extent, tryptophan.
Which enzyme reduces dihydrofolate to its functionally active form, tetrahydrofolate?
Dihydrofolate reductase.
Which step in the formation of 5-methyl THF from THF is irreversible?
The conversion of 5,10-methylene THF to 5-methyl THF by methylene reductase.
Which enzyme regenerates THF from 5-methyl THF?
Methionine synthase.
Methionine synthase requires what cofactor for proper activity?
Vitamin B12 (in the form of methylcobalamin).
Which amino acid can be derived from the action of serine hydroxymethylase on a serine molecule?
Glycine.
Which coenzyme is required for activity of Dopa decarboxylase?
Pyridoxal phosphate (PLP).
Which coenzyme is required for activity of serine hydroxymethylase?
Pyridoxal phosphate (PLP).
Which tetrahydrofolate (THF) derivative is most abundant in plasma?
5-methyl THF.
What is the product of the reaction catalyzed by serine dehydratase?
Pyruvate.
Which birth defect is associated with low folate during pregnancy?
Spina bifida.
Which folate analogue interferes with the growth of rapidly growing cells by interfering with pyrimidine synthesis?
Methotrexate.
Which analgue of p-aminobenzoic acid can block synthesis of folate in bacteria but not in humans?
Sulfanilamides.
Which compound directly derived from methionine is involved in the transfer of methyl groups?
S-adenosylmethionine.
S-adenosylmethionine converts into which compound upon donation of its methyl group?
S-adenosylhomocysteine.
What cofactor is required for the conversion of norepinephrine to epinephrine?
S-adenosylmethionine.
Which amino acids are directly involved in the synthesis of creatine?
Glycine, arginine and methionine.
What are two ways in which free homocysteine can be converted to methionine?
A methyl group can be transferred from 5-methyl THF or a methyl group can be transferred from choline.
What is the only enzyme that has the ability to regenerate THF from methyl-THF?
Methionine synthase.
Dietary deficiency of which vitamin can lead to a deficiency in functional folate?
Vitamin B12.
Which major component of bile acids is derived from cysteine?
Taurine.
Which amino acids serve as precursors for the synthesis of cysteine?
Methionine and serine.
What are the products of the breakdown of cystathione by the enzyme cystathionase?
Cysteine and alpha-ketobutyrate.
Increased levels of which non-protein amino acid are associated with folate metabolism abnormalities?
Homocysteine.
True or False. Increased levels of homocysteine are associated with an increased risk of arterial disease.
True.
Which branched chain amino acids are preferentially metabolized for the production of ATP in muscle?
Valine, leucine and isoleucine.
Which amino acid can be directly transaminated to pyruvate for gluconeogenesis in the liver?
Alanine.
Which amino acid is used by the liver for either the production of ammonia or the synthesis of glutamate?
Glutamine.
What is the function of glutaminase in the kidneys?
Glutaminase generates glutamate and ammonium ions from glutamine. In the kidneys, this serves to increase the amount of ammonium ions excreted.
Which amino acid is preferentially used for energy production in the intestines?
Glutamine.
