Defects in MOCS1 are the cause of molybdenum cofactor deficiency type A (MOCOD type A) [MIM:252150]; an autosomal recessive disease which leads to the pleiotropic loss of all molybdoenzyme activities and is characterized by severe neurological damage, neonatal seizures and early childhood death.
In the C-terminal section; belongs to the moaC family. In the N-terminal section; belongs to the moaA/nifB/pqqE family.
Isoform MOCS1A, isoform 2 and isoform 3 are probably thiocarboxylated at their C-terminus. Thiocarboxylation probably plays a central role in molybdenum cofactor biosynthesis, since mutagenesis of the last 2 Gly residues of isoform MOCS1A abolishes the catalytic activity of the enzyme. Thiocarboxylation is absent in isoform MOCS1B, which lacks the C-terminal Gly residue.