高粱叶片磷酸烯醇式丙酮酸羧化酶溶液构象状态的紫外差示吸收光谱研究

PEP诱导产生的差光谱在237nm是一强负峰,在252nm附近呈宽负峰。Mg~(2+)产生的差光谱在275nm附近为正的阔峰,在237nm处为一负峰。PEP、Mg~(2+)共同与酶作用的差光谱在263nm附近呈宽的负峰。正效应剂G6P、Gly及GG分别存在条件下PEP羧化酶的差光谱亦各具明显差异,在270nm以下光区内尤其显著。在284nm和291nm为两个负峰,Gly诱导的峰强度大于G6P的,而GG复合效应剂对此两峰的影响表现很大的协同作用。Mal作用于酶的差光谱在246nm处有一负峰。

ULTRAVIOLET ABSORPTION DIFFERENCE SPECTRA STUDIES ON CONFORMATIONAL STATES OF SORGHUM LEAF PHOSPHOENOLPYRUVATE CARBOXYLASE IN SOLUTION

Ultraviolet absorption difference spectra of sorghum leaf PEP carboxylase provoked by adding various ligands were recorded. The spectrum induced by substrate PEP shows a strong negative peak at 237 nm and a broad negative band near 252nm. Mg~(2+), which is required for carboxylation of PEP, induced a spectrum with a wide positive absorption band whose maximum is located at 275nm, and a negative peak at 237nm. When PEP and Mg~(2+) were added together to the enzyme solution, there appeared a spectrum with a minimum near 263nm.Activators G6P, Gly and G6P-Gly produced different effects on the absorption spectrum of PEP carboxylase. All the three spectra are characterized by two minima at 284nm and 291nm, and the values of them show that G6P and Gly exert great cooperative effect on enzyme absorption.The absorption spectrum of the enzyme also changed markedly in the presence of malate, the inhibitor of PEP carboxylase.All these results supported the conclusion that multiple conformational states of PEP carboxylase from sorghum leaves can be elicited by substrates, metal ions and effectors.