FUNCTION AND ASSEMBLY OF CO2 ASSIMILATORY ENZYMES

二氧化碳转化为有机物的初级同化作用被催化 被地球上发现的最丰富的蛋白质D-核酮糖1，5-二磷酸 （RuBP）羧化酶。 在合适的条件下，酶也可以表现出 作为内部单加氧酶并催化氧固定反应。 的 相同的多肽链催化羧化酶和加氧酶活性， 使这种酶成为已知能够 催化两种不同的反应 此外，单独的活动 代表了细胞内两种竞争途径的第一反应， 新陈代谢. 因此，这项研究代表了一个不寻常的机会， 在酶和分子水平上控制显著的代谢 事件 我们最近的研究表明， 不同地调节每个活动。 因此，拟议工作的一部分 将寻求扩大这些研究，主要是结构简单， 细菌酶，目的是选择性地改变或修饰一种 活动，以排除其他。 为此，我们已制定了 重要的观察是，黄色荧光“辅因子”可以 仅参与加氧酶反应。 我们将分离，提纯， 表征该材料并确定其在加氧酶中的作用 反应 此外，利用蛋白质化学技术， 标记和酶动力学，我们将继续研究 这个双功能酶的活性位点和调节位点。 最后，我们将研究RuBP的合成和组装 羧化酶/加氧酶，因为这种酶可以包含高达50%的羧化酶/加氧酶。 相关细菌和真核生物的可溶性蛋白质， 分布在离散的细胞器中。

The primary assimilation of carbon dioxide into organic matter is catalyzed by the most abundant protein found on earth, D-ribulose 1,5-disphosphate (RuBP) carboxylase. Under suitable conditions, the enzyme may also behave as an internal monooxygenase and catalyze an oxygen fixation reaction. The same polypeptide chain catalyzes both carboxylase and oxygenase activities, making this enzyme one of the few proteins known to be capable of catalyzing two distinct reactions. Moreover, the separate activities represent the first reactions of two competing pathways in cellular metabolism. This study thus represents an unusual opportunity to relate control at the enzymic and molecular level to significant metabolic events. Our recent work has shown that it may be possible to differentially regulate each activity. Thus, part of the proposed work will seek to extend these studies, primarily with a structurally simple bacterial enzyme, with the goal of selectively altering or modifying one activity to the exclusion of the other. Toward this end, we have made the significant observation hat a yellow, fluorescent "cofactor" may participate in only the oxygenase reaction. We will isolate, purify and characterize this material and detemine its role in the oxygenase reaction. Moreover, using techniques of protein chemistry, affinity labeling, and enzyme kinetics, we will continue to investigate the nature of the active site and the regulator sites of this bifunctional enzyme. Lastly, we will investigate the synthesis and assembly of RuBP carboxylase/oxygenase, since this enzyme may comprise up to 50 percent of the soluble protein of relevant bacteria and eucaryotes, where it is localized in discrete organelles.