Department of Biochemistry, University of California, Riverside, California 92521.
Plant Physiol. 1988 Jun;87(2):443-6. doi: 10.1104/pp.87.2.443.
The binding of phosphoenolpyruvate, malate, and glucose 6-phosphate to phosphoenolpyruvate carboxylase purified from Crassula argentea Thunb. was measured using both the intrinsic tryptophan fluorescence of the enzyme and the extrinsic fluorescence of the complex of 8-anilino-1-napthalenesulfonate with the enzyme. It was found that the substrate phosphoenolpyruvate can bind in the absence of magnesium but is bound in greater quantities and more tightly when magnesium is present. Malate reduces the binding of phosphoenolpyruvate, while glucose 6-phosphate increases the binding of the substrate. Glucose 6-phosphate requires magnesium to bind to the enzyme, while malate does not. The general trends from the binding experiments using fluorescence methods were confirmed by activity determinations using assays performed in the absence of magnesium.
用酶的固有色氨酸荧光和酶与 8-苯胺-1-萘磺酸复合物的外显荧光测量了从 Crassula argentea Thunb. 中纯化的磷酸烯醇丙酮酸羧化酶与磷酸烯醇丙酮酸、苹果酸和葡萄糖 6-磷酸的结合。结果发现，尽管没有镁，但是当镁存在时，基质磷酸烯醇丙酮酸可以结合并且结合更多和更紧密。苹果酸降低了磷酸烯醇丙酮酸的结合，而葡萄糖 6-磷酸增加了底物的结合。葡萄糖 6-磷酸需要镁才能与酶结合，而苹果酸不需要。荧光方法的结合实验的一般趋势通过在没有镁的情况下进行的测定中使用活性测定得到了证实。
