Question

Which three amino acids are substrates or products of serine hydroxymethyltransferase?

Short answer

Serine, glycine, and THF are three amino acids substrates of serine hydroxymethyltransferase.

Step-by-step solution

Synthesis of thymine

THF acquires C1 units in converting serine to glycine by serine Hydroxymethyltransferase, glycine cleavage, and histidine breakdown. The C1 units carried by THF are used in the synthesis of thymine nucleotides and the synthesis of methionine from homocysteine.

 Step 2: Conversion of threonine.

Threonine can also be converted directly to glycine and acetaldehyde (which is subsequently oxidized to acetyl-CoA) via a reaction that breaks threonine’s Cα—Cβ bond. This PLP-dependent reaction is catalyzed by serine hydroxymethyltransferase, the same enzyme that adds a hydroxymethyl group to glycine to produce serine, promoting the latter process; supplemental folate helps prevent diseases associated with abnormally high homocysteine levels.