Catalytic Mechanisms and Biological Roles of Enzymes Involved in Energy Metabolism

在我的研究中，我了解酶是如何工作的。酶的工作是加速特定的反应，使反应能够在活细胞所需的时间尺度上发生。我们通过生长酶的晶体来研究酶，类似于盐瓶或钻石中的盐晶体。利用我们的晶体，我们能够得到酶及其作用分子的图像，通过观察这些图像，我们形成了酶如何工作的想法。我们通过改变酶的结构来测试我们的想法，并发现它是否仍然有效。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的反应使用三种分子：核苷酸三磷酸，琥珀酸和辅酶A（CoA）。从这些，酶使磷酸和核苷酸二磷酸，以及琥珀酰辅酶A。我们想知道这种酶是如何结合这些不同的分子的。到目前为止，我们已经有了辅酶A和核苷酸的酶的图片。辅酶A与核苷酸结合的位置相距甚远。在CoA附近，有一个酶的残基，在反应过程中被磷酸化，这个残基位于酶环的顶端。我们的想法是，酶摆动这个环，使磷酰基在两个结合位点之间穿梭。通过这种方式，酶能够将一个位点发生的事情与另一个位点发生的事情联系起来。它能够利用两个独立的结合位点来结合它所作用的分子，这可能是酶必须结合三种底物并释放三种产物的一般机制。我们的研究将有助于对酶及其工作原理的基本了解。最近，一个研究小组确定了患有贫血的患者，因为他们有一种与琥珀酰辅酶A合成酶相互作用的酶的缺陷形式。使用我们在实验室生产的酶，我们表明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在产生足够的血红素以预防贫血方面很重要。

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.