Phosphoenol-3-bromopyruvate. A mechanism-based inhibitor of phosphoenolpyruvate carboxylase from maize.
Phosphoenol-3-bromopyruvate. A mechanism-based inhibitor of phosphoenolpyruvate carboxylase from maize.
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磷酸烯醇-3-溴丙酮酸酯。
DOI：
10.1016/s0021-9258(18)33318-0
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发表时间：
1982
期刊：
影响因子：
--
通讯作者：
E. Diaz
中科院分区：
文献类型：
--
作者：
M. O'Leary;E. Diaz
磷酸烯醇-3-溴丙酮酸是玉米磷酸烯醇式丙酮酸羧化酶(Ki=30微米)的竞争性抑制剂(相对于磷酸烯醇式丙酮酸)，条件是避免酶与抑制剂的预孵育。如果在Mn2+和HCO3(-)的存在下，酶与抑制剂预孵育，则在约1h内完全失活，酶的失活是一级的，相对于抑制剂是饱和的，表观米氏常数为67.5微米，在高浓度的抑制剂13.4min时，半衰期为13.4min。低浓度的HCO3(-)对该酶的失活有抑制作用，且失活速度慢得多。在H14CO3(-)和Mn2+存在下，酶与磷酸-3-溴丙酮酸孵育，然后用NaBH4处理，导致14C进入失活的酶中。如果省略NaBH4处理，该酶将失活，但不会将14C并入失活产物中。磷酸烯醇-3-溴丙酮酸似乎是磷酸烯醇式丙酮酸羧化酶的机理失活剂，可能是因为酶催化转化为3-溴草酸乙酸酯，从而使酶烷化。
Phosphoenol-3-bromopyruvate is an excellent competitive inhibitor (versus phosphoenolpyruvate) of maize phosphoenolpyruvate carboxylase (Ki = 30 microM), provided that preincubation of enzyme with inhibitor is avoided. If the enzyme is preincubated with inhibitor in the presence of Mn2+ and HCO3(-), complete inactivation occurs over the course of about 1 h. The inactivation is first order in enzyme and is saturable with respect to inhibitor, with an apparent Michaelis constant of 67.5 microM and a half-life at high inhibitor concentration of 13.4 min. The inactivation is inhibited by phospholactate and is much slower at low HCO3(-) concentration. Incubation of the enzyme with phosphoenol-3-bromopyruvate in the presence of H14CO3(-) and Mn2+ followed by treatment with NaBH4 leads to incorporation of 14C into the inactive enzyme. If treatment with NaBH4 is omitted, the enzyme is inactivated, but no 14C is incorporated into the inactive product. It appears that phosphoenol-3-bromopyruvate is a mechanism-based inactivator of phosphoenolpyruvate carboxylase, probably because of enzyme-catalyzed conversion to 3-bromooxalacetate, which alkylates the enzyme.