Humm A, Fritsche E, Steinbacher S
Max-Planck-Institut für Biochemie, Abt. Strukturforschung, Martinsried, Germany.
Biol Chem. 1997 Mar-Apr;378(3-4):193-7.
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.
L-精氨酸：甘氨酸脒基转移酶（AT）通过生成胍基乙酸（肌酸的直接前体）催化肌酸生物合成中的关键步骤。人源该酶的X射线结构显示出一种具有ββαβ-模块五重假对称的新型折叠。这些模块包围着篮状结构的活性位点隔室。AT的活性位点位于一个非常狭窄通道的底部，包含一个由半胱氨酸-组氨酸-天冬氨酸残基组成的催化三联体。转脒基反应遵循乒乓机制，并伴随着较大的构象变化。在催化过程中，脒基共价连接到活性位点的半胱氨酸上，生成一个脒基-半胱氨酸中间体。
