Structure and reaction mechanism of L-arginine:glycine amidinotransferase.
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Humm A, Fritsche E, Steinbacher S
Structure and reaction mechanism of L-arginine:glycine amidinotransferase.
Biol Chem. 1997 Mar-Apr;378(3-4):193-7.
- PubMed ID
- 9165070 [ View in PubMed]
- Abstract
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.