PylC enzyme catalyzes
PylC functions as ATP-dependent ligase catalyzing second step of pyrrolysine pathway, condensation of (3R)-3-methyl-D-ornithine with second L-lysine molecule via amide bond formation between ornithine carboxylate and lysine epsilon-amino group, producing N6-((2R,3R)-3-methylornithyl)-lysine. Mechanism employs ATP to activate carboxylate as acyl-adenylate intermediate then nucleophilic attack by lysine amine, similar to glutathione synthesis. PylC structure resembles D-alanine-D-alanine ligase fold. Deletion of pylC accumulates methylornithine and ablates pyrrolysine formation preventing amber
Ref: NCBI Bookshelf, Ligases: PylC Condensation Reaction in Pyrrolysine Pathway
