FUNCTION AND ASSEMBLY OF CO2 ASSIMILATORY ENZYMES

二氧化碳转化为有机物的初级同化作用是催化的 由地球上发现的最丰富的蛋白质D-核酮糖1，5-二磷酸 (RuBP)羧基酶。在适当的条件下，这种酶也可以表现出 作为一种内部单加氧酶并催化氧固定反应。这个 相同的多肽链催化羧基酶和加氧酶活性， 使这种酶成为已知的为数不多的能够 催化两种截然不同的反应。此外，单独的活动 代表细胞内两条相互竞争的通路的第一反应 新陈代谢。因此，这项研究代表了一个不寻常的机会来联系 在酶和分子水平上控制显著代谢 事件。我们最近的研究表明，有可能 对每一项活动进行不同的监管。因此，拟议工作的一部分 将寻求扩展这些研究，主要是通过一个结构简单的 细菌酶，目的是选择性地改变或修饰一种 排挤他人的活动。为此，我们制定了 重要的观察表明，黄色的、荧光的“辅因子”可能 只参与加氧酶反应。我们将分离、提纯和 对这种物质进行表征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，亲和力 标记和酶动力学，我们将继续研究其性质 这种双功能酶的活性部位和调节部位。 最后，我们将研究RuBP的合成和组装 羧基酶/加氧酶，因为这种酶可能包含高达50%的 相关细菌和真核生物的可溶性蛋白质，其所在位置 定位于不连续的细胞器。

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.