The Catalytic Serine of <i>meta</i>-Cleavage Product Hydrolases Is Activated Differently for C–O Bond Cleavage Than for C–C Bond Cleavage
作者:Antonio C. Ruzzini、Geoff P. Horsman、Lindsay D. Eltis
DOI:10.1021/bi300663r
日期:2012.7.24
triad to catalyze hydrolysis via an acyl–enzyme intermediate. BphD, which catalyzes the hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) in biphenyl degradation, catalyzed the hydrolysis of an ester analogue, p-nitrophenyl benzoate (pNPB), with a kcat value (6.3 ± 0.5 s–1) similar to that of HOPDA (6.5 ± 0.5 s–1). Consistent with the breakdown of a shared intermediate, product analyses
间位裂解产物(MCP)水解酶催化细菌对芳香族化合物的有氧分解代谢中的C–C键裂变。这些酶利用Ser-His-Asp三联体通过酰基酶中间体催化水解。BphD在联苯降解中催化2-羟基-6-氧代-6-苯基六-2,4-二烯酸(HOPDA)的水解,并催化酯类似物对硝基苯甲酸苯酯(pNPB)的水解。k cat值(6.3±0.5 s –1)与HOPDA(6.5±0.5 s –1)相似)。与共有中间体的分解一致,产物分析表明,BphD催化HOPDA和pNPB的甲醇分解,将产物以相似的比例分配给苯甲酸和苯甲酸甲酯。在短的伯醇(甲醇>乙醇>正丙醇)存在下,HOPDA的周转速度提高了4倍,这表明在催化过程中脱酰作用是限速的。在HOPDA的稳态水解中,k cat / K m值与甲醇浓度无关,而k cat和K m值随甲醇浓度增加。该结果与亲核催化的简单模型一致。尽管在甲醇浓度> 250 mM时无法用pNPB饱和该酶,但k