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光合细菌红螺菌中二磷酸核酮糖羧化酶的动力学研究。

A kinetic study of ribulose bisphosphate carboxylase from the photosynthetic bacterium Rhodospirillum rubrum.

作者信息

Christeller J T, Laing W A

出版信息

Biochem J. 1978 Aug 1;173(2):467-73. doi: 10.1042/bj1730467.

Abstract

The activation kinetics of purified Rhodospirillum rubrum ribulose bisphosphate carboxylase were analysed. The equilibrium constant for activation by CO(2) was 600 micron and that for activation by Mg2+ was 90 micron, and the second-order activation constant for the reaction of CO(2) with inactive enzyme (k+1) was 0.25 X 10(-3)min-1 . micron-1. The latter value was considerably lower than the k+1 for higher-plant enzyme (7 X 10(-3)-10 X 10(-3)min-1 . micron-1). 6-Phosphogluconate had little effect on the active enzyme, and increased the extent of activation of inactive enzyme. Ribulose bisphosphate also increased the extent of activation and did not inhibit the rate of activation. This effect might have been mediated through a reaction product, 2-phosphoglycolic acid, which also stimulated the extent of activation of the enzyme. The active enzyme had a Km (CO2) of 300 micron-CO2, a Km (ribulose bisphosphate) of 11--18 micron-ribulose bisphosphate and a Vmax. of up to 3 mumol/min per mg of protein. These data are discussed in relation to the proposed model for activation and catalysis of ribulose bisphosphate carboxylase.

摘要

对纯化的深红红螺菌核酮糖二磷酸羧化酶的激活动力学进行了分析。CO₂激活的平衡常数为600微摩尔,Mg²⁺激活的平衡常数为90微摩尔,CO₂与无活性酶反应的二级激活常数(k⁺¹)为0.25×10⁻³分钟⁻¹·微摩尔⁻¹。后一数值明显低于高等植物酶的k⁺¹(7×10⁻³ - 10×10⁻³分钟⁻¹·微摩尔⁻¹)。6 - 磷酸葡萄糖酸对活性酶影响很小,但增加了无活性酶的激活程度。核酮糖二磷酸也增加了激活程度且不抑制激活速率。这种效应可能是通过反应产物2 - 磷酸乙醇酸介导的,2 - 磷酸乙醇酸也刺激了该酶的激活程度。活性酶的Km(CO₂)为300微摩尔CO₂,Km(核酮糖二磷酸)为11 - 18微摩尔核酮糖二磷酸,Vmax高达每毫克蛋白质3微摩尔/分钟。结合所提出的核酮糖二磷酸羧化酶激活和催化模型对这些数据进行了讨论。

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