Type III Pyridoxal 5-phosphate (PLP)-Dependent Enzymes, YBL036c-like proteins
This family contains mostly uncharacterized proteins, widely distributed among eukaryotes, bacteria and archaea, that bear similarity to the yeast hypothetical protein YBL036c, which is homologous to a Pseudomonas aeruginosa gene that is co-transcribed with a known proline biosynthetic gene. YBL036c is a single domain monomeric protein with a typical TIM barrel fold. It binds the PLP cofactor and has been shown to exhibit amino acid racemase activity. The YBL036c structure is similar to the N-terminal domain of the fold type III PLP-dependent enzymes, bacterial alanine racemase and eukaryotic ornithine decarboxylase, which are two-domain dimeric proteins. The lack of a second domain in YBL036c may explain limited D- to L-alanine racemase or non-specific racemase activity.