Monomeric sarcosine oxidase (MSOX) catalyses the oxidative demethylation of sarcosine (N-methylglycine) to form glycine and formaldehyde. Sarcosine is a common soil metabolite that can act as the sole source of carbon and energy for many microorganisms capable of expressing sarcosine oxidase.
MSOX is part of a family of enzymes which contain flavin (FAD covalently attached to the protein via Cys315) and catalyse the oxidation of various secondary and tertiary amino acids.
Despite the vast amount of research that has been done on these enzymes, the exact mechanism remains elusive. There are three proposals: polar, hydride and single electron transfer. To date, there is little evidence to suggest one over the other.
The mechanism by which Cys315 becomes attached to FAD involves His45 and Arg49 [PMID:10368302] and is thought to be autocatalytic. The formation of the covalent FAD adduct is not shown in this entry.
Defined by 7 residues: HIS:B-45THR:B-48ARG:B-49LYS:B-265HIS:B-269CYS:B-315LYS:B-348