底物类似物对牛肝果糖-1,6-二磷酸酶的抑制作用。

Inhibition of bovine hepatic fructose-1,6-diphosphatase by substrate analogs.

作者信息

Marcus C J

出版信息

J Biol Chem. 1976 May 25;251(10):2963-6.

Abstract

Purified bovine hepatic fructose-1,6-diphosphatase, which exhibits maximal activity at neutral pH, is competitively inhibited by several analogs of its substrate, fructose 1,6-diphosphate. These include glucose 1,6-diphosphate (Ki = 9.4 X 10(-5) M), hexitol 1,6-diphosphate (Ki = 2.3 X 10(-4) M), and 2,5-anhydro-D-mannitol 1,6-diphosphate (Ki = 3.3 X 10(-8) M), and 2,5-anhydro-D-glucitol 1,6-diphosphate (Ki = 5.5 X 10(-7) M). The Ki values for both 2,5-anhydro-D-mannitol 1,6-diphosphate and 2,5-anhydro-D-glucitol 1,6-diphosphate are lower than the Km of 1.4 X 10(-6) M for fructose 1,6-diphosphate. Since 2,5-anhydro-D-mannitol 1,6-diphosphate is an analog of the beta anomer of fructose 1,6-diphosphate and 2,5-anhydro-D-glucitol 1,6-diphosphate is an analog of the alpha anomer, the lower Ki for the mannitol analog may indicate that the beta anomer of fructose 1,6-diphosphate, which predominates in solution, is the true substrate. The substrate analog 1,5-pentanediol diphosphate inhibits slightly (K0.5 = 5 X 10(-3) M), but 1,4-cyclohexyldiol diphosphate does not. The Ki for product inhibition by sodium phosphate is 9.4 X 10(-3) M. 2,5-Anhydro-D-mannitol 1,6-diphosphate and alpha-D-glucose 1,6-diphosphate are substrates at pH 9.0, but not at pH 6.5.

摘要

纯化的牛肝果糖-1,6-二磷酸酶在中性pH值下表现出最大活性，其受到几种底物类似物果糖1,6-二磷酸的竞争性抑制。这些类似物包括葡萄糖1,6-二磷酸（Ki = 9.4×10⁻⁵ M）、己糖醇1,6-二磷酸（Ki = 2.3×10⁻⁴ M）、2,5-脱水-D-甘露糖醇1,6-二磷酸（Ki = 3.3×10⁻⁸ M）以及2,5-脱水-D-葡萄糖醇1,6-二磷酸（Ki = 5.5×10⁻⁷ M）。2,5-脱水-D-甘露糖醇1,6-二磷酸和2,5-脱水-D-葡萄糖醇1,6-二磷酸的Ki值均低于果糖1,6-二磷酸的Km值1.4×10⁻⁶ M。由于2,5-脱水-D-甘露糖醇1,6-二磷酸是果糖1,6-二磷酸β异头物的类似物，而2,5-脱水-D-葡萄糖醇1,6-二磷酸是α异头物的类似物，甘露醇类似物较低的Ki值可能表明在溶液中占主导的果糖1,6-二磷酸β异头物是真正的底物。底物类似物1,5-戊二醇二磷酸有轻微抑制作用（K0.5 = 5×10⁻³ M），但1,4-环己二醇二磷酸无抑制作用。磷酸钠对产物抑制的Ki值为9.4×10⁻³ M。2,5-脱水-D-甘露糖醇1,6-二磷酸和α-D-葡萄糖1,6-二磷酸在pH 9.0时是底物，但在pH 6.5时不是。