L-arginine:glycine amidinotransferase and similar proteins
This subfamily includes eukaryotic L-arginine:glycine amidinotransferase (EC 2.1.4.1; also called glycine amidinotransferase or arginine-glycine amidinotransferase or arginine-glycine transamidinase or AT or AGAT) involved in creatine biosynthesis. L-arginine:glycine amidinotransferase (AGAT) catalyzes the committed step in creatine biosynthesis by formation of guanidinoacetic acid, the immediate precursor of creatine. Creatine plays a vital role in energy metabolism in muscle tissues, and may play a role in embryonic and central nervous system development and may be involved in the response to heart failure by elevating local creatine synthesis. This subfamily also contains bacterial proteins that include the virulence-associated protein HsvA from the fire blight pathogen Erwinia amylovora shown to be a polyamine amidinotransferase, and cyanobacterial SxtG, an amidinotransferase involved in the biosynthesis of paralytic shellfish toxins. The active sites of these enzymes are located in the core of the proteins at the base of a long, narrow substrate access channel. HsvA has a novel acceptor substrate specificity, with a clear preference for linear polyamines, especially putrescine and spermidine, as the amidino acceptor substrate. SxtG has a broad substrate promiscuity, operating on a wide variety of substrates and preferring alpha-amino ketones and alpha-amino methyl esters over alpha-amino acids.
Jiyao W et al.(2023). "The conserved domain database in 2023.",