Catalytic Mechanisms and Biological Roles of Enzymes Involved in Energy Metabolism

在我的研究中，我了解了酶是如何工作的。酶的作用是加速特定的反应，这样反应就能在活细胞所需的时间尺度上发生。我们通过培养一种酶的晶体来研究它，类似于盐瓶或钻石中的盐晶体。利用我们的晶体，我们能够得到酶和它作用的分子的照片。通过观察这些图片，我们对酶的工作原理有了一些了解。我们通过改变酶的结构来检验我们的想法，看看它是否仍然有效。我们研究的一种酶叫做琥珀酰辅酶a合成酶。形成琥珀酰辅酶A的反应需要三个分子：三磷酸核苷酸、琥珀酸盐和辅酶A （CoA）。从这些，酶产生磷酸和二磷酸核苷酸，以及琥珀酰辅酶a。我们想要发现这种酶是如何结合这些非常不同的分子的。到目前为止，我们已经有了酶与辅酶a和核苷酸的图片。酶上辅酶a结合的地方和核苷酸结合的地方相隔很远。在辅酶a附近，酶的残基在反应中被磷酸化这个残基位于酶环的顶端。我们的想法是，这种酶摆动这个环，在两个结合位点之间穿梭磷酸化基团。通过这种方式，酶能够将一个位点上发生的事情与另一个位点上发生的事情联系起来。它能够为作用于它的分子使用两个独立的结合位点。这可能是必须结合三种底物并释放三种产物的酶的一般机制。我们的研究将有助于对酶及其工作原理的基本了解。最近，一个研究小组发现了一些患有贫血的患者，因为他们有一种与琥珀酰辅酶a合成酶相互作用的酶有缺陷。使用我们在实验室生产的酶，我们证明了他们的酶的缺陷形式不能与琥珀酰辅酶a合成酶相互作用。现在我们正试图了解这些酶是如何相互作用的，以及为什么这种相互作用对产生足够的血红素来预防贫血很重要。

In my research, I learn how enzymes work. An enzyme's job is to speed up a specific reaction, so that the reaction can happen on the time-scale required by a living cell. We study an enzyme by growing crystals of it, similar to crystals of salt in a salt shaker or a diamond. Using our crystals, we are able to get pictures of the enzyme with the molecules it works on. From looking at these pictures, we form ideas of how the enzyme works. We test our ideas by changing the structure of the enzyme and discovering whether it still works. One enzyme we investigate is called succinyl-CoA synthetase. The reaction forming succinyl-CoA uses three molecules: nucleotide triphosphate, succinate and coenzyme A (CoA). From these, the enzyme makes phosphate and nucleotide diphosphate, as well as succinyl-CoA. We would like to discover how the enzyme is able to bind these very different molecules. So far, we have pictures of the enzyme with CoA and with nucleotides. The places on the enzyme where CoA binds and where the nucleotides bind are far apart. Near the CoA, there is a residue of the enzyme that gets phosphorylated during the reaction and this residue is at the tip of a loop of the enzyme. Our idea is that the enzyme swings this loop to shuttle the phosphoryl group between the two binding sites. In this way, the enzyme is able to connect what is happening at one site to what happens at the other. It is able to use two separate binding sites for the molecules it acts on. This may be a general mechanism for enzymes that have to bind three substrates and release three products. Our research will contribute to the basic understanding of enzymes and how they work. Recently, a research group identified patients who suffered from anemia because they had a faulty form of an enzyme that interacts with one form of succinyl-CoA synthetase. Using enzyme that we produced in the lab, we showed that the faulty form of their enzyme could not interact with succinyl-CoA synthetase. Now we are trying to learn how these enzymes interact and why the interaction is important in producing enough heme to prevent anemia.