Structure and reaction mechanism of L-arginine:glycine amidinotransferase.
L-Arginine:glycine amidinotransferase (AT) catalyzes the committed step in creatine biosynthesis by formation of guanidinoacetic acid, the direct precursor of creatine. The X-ray structure of the human enzyme shows a novel fold with fivefold pseudosymmetry of beta beta alphabeta-modules. These modules enclose the active site compartment of the basket-like structure. The active site of AT lies at the bottom of a very narrow channel and contains a catalytic triad with the residues Cys-His-Asp. The transamidination reaction follows a ping-pong mechanism and is accompanied by large conformational changes. During catalysis the amidino group is covalently attached to the active site cysteine to give an amidino-cysteine intermediate.
Humm
A
A
Max-Planck-Institut für Biochemie, Abt. Strukturforschung, Martinsried, Germany.
Fritsche
E
E
Steinbacher
S
S
D000579:Amidinotransferases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D003460:Crystallization; D006801:Humans; D017434:Protein Structure, Tertiary
D000579:Amidinotransferases; C020681:glycine amidinotransferase