STRUCTURE AND FUNCTION OF HISTIDINE DECARBOXYLASE

黄曲霉组氨酸脱羧酶的结构与功能关系 乳杆菌30a将用X射线衍射法进行研究。这是 一种可诱导的细菌氨基酸脱羧酶，发现与 哺乳动物的消化道。它会产生大量的 神经递质，组胺，虽然生理意义 这一点还没有得到很好的理解。这种酶具有许多独特的 性质，利用共价键合的丙酮酰部分代替 吡哆醛-5‘-磷酸。丙酮酰假体基团起源于一种 自动激活过程中的内部丝氨酸残留量 丝氨酸-丝氨酸肽键的断裂。 我们有野生型组氨酸脱羧酶的晶体，它的酶原，和 天然酶的活性部位类似物。我们最近计算了一个 野生型酶的3埃分辨电子密度图 已经成功地用来产生这种酶的链跟踪。 这是唯一的氨基酸脱羧酶或酮酸依赖酶 哪些X射线结构数据是可用的。其他高分辨率数据 将为该系统收集数据，并对最终的模型进行改进。这个 将对酶原形式进行相应的结构研究 并对这两种精制结构进行比较，研究其独特的作用机制。 这些酶的激活。活性中心残基的化学修饰 野生型酶Will活性部位类似物的结构分析 与相关系统上的氨基酸序列数据结合使用 研究这些丙酮酰依赖组氨酸的作用机制 脱羧酶。吡哆醛-5‘-磷酸的新结晶学研究 依赖形式的组氨酸脱羧酶也将在 这段授权期。

The structure-function relationships of histidine decarboxylase from Lactobacillus 30a will be studied by x-ray diffraction techniques. This is an inducible bacterial amino acid decarboxylase found associated with the digestive tract of mammals. It produces large amounts of the neurotransmitter, histamine, although the physiological significance of this is not well understood. The enzyme possesses a number of unique properties, utilizing a covalently bound pyruvoyl moiety instead of pyridoxal-5'-phosphate. The pyruvoyl prosthetic group originates from an internal serine residue during an auto-activation process involving cleavage of a serine-serine peptide bond. We have crystals of wild-type histidine decarboxylase, its proenzyme, and of an active site analog of the native enzyme. We have recently computed a 3 angstroms resolution electron density map for the wild-type enzyme which has been successfully used to produce a chain tracing for this enzyme. This is the only amino acid decarboxylase or keto acid dependent enzyme for which x-ray structural data is available. Additional high resolution data will be collected for this system and the resulting model refined. The corresponding structural studies on the proenzyme form will be conducted and the two refined structures compared to study the unique mechanism of activation in these enzymes. Chemical modification of active site residues and structural analysis of active site analogs of the wild-type enzyme will be used in conjunction with amino acid sequence data on related systems to study the mechanism of action of these pyruvoyl dependent histidine decarboxylases. New crystallographic studies of pyridoxal-5'-phosphate dependent forms of histidine decarboxylase will also be undertaken during this grant period.