Mechanisms of polyketide, amino acid and Polypeptide biosynthesis

拟议的生物有机化学和天然产物化学研究的主要目标包括：a)开发研究次生代谢(特别是聚酮和多肽的生物合成)的新方法；以及b)研究参与氨基酸和多肽代谢的酶的机制和抑制。该计划结合了有机化学(如合成、光谱分析)和生物化学(如分子生物学、蛋白质表征、酶抑制、核磁共振溶液结构以及与之合作的蛋白质X射线结晶学)中使用的方法。该计划的一部分侧重于真菌组装聚酮的方式，聚酮是一类通常由醋酸酯制成的次生代谢物，通常具有重要的生物活性。特别是，将检查洛伐他汀的组装细节，洛伐他汀是一种降胆固醇药物，也是辛伐他汀(Zocor)的前体。这种分子的构建需要聚酮合成酶(PKS)酶LovB和烯醇还原酶Lovc，这两种酶共同在35个高度编程的步骤中产生洛伐他汀的大部分骨架。我们将研究这种非凡的分子机器的一步一步的转变，目的是阐明其机制并产生新的药物类似物。类似的方法将用于研究其他三种具有生物活性的真菌聚酮化合物的生物合成。该计划的第二部分针对细菌素，细菌素是由天然存在于食品中的细菌产生的抗菌肽。它们比传统抗生素有效许多个数量级，对目前治疗耐药的病原体有效。特别是，为了了解构效关系和制造更稳定的衍生物，将研究抗生素的化学合成，这是一类含有单硫代羊毛硫环的细菌素。目标包括乳糖素3147和加里德明。另一个方面涉及测定苏尿酸的生物合成细节，这种物质对危险的病原体艰难梭菌核型027有活性。他们的3D结构也将通过新的方法进行检查

The major objectives of the proposed research in bioorganic chemistry and natural products chemistry include: a) development of new approaches to study secondary metabolism (especially polyketide and polypeptide biosynthesis); and b) study of the mechanism and inhibition of enzymes involved in amino acid and peptide metabolism. The program involves a combination of methods used in organic chemistry (e.g. synthesis, spectroscopic analysis) and biochemistry (e.g. molecular biology, protein characterization, enzyme inhibition, NMR solution structures and, in collaboration, x-ray crystallography of proteins). One part of the program focuses on the way fungi assemble polyketides, a class of secondary metabolites typically built from acetate, that often have important biological activity. In particular, the details of assembly of lovastatin, a cholesterol-lowering agent and precursor to the drug simvastatin (Zocor) will be examined. Construction of this molecule requires the polyketide synthase (PKS) enzyme LovB and the enoyl reductase enzyme LovC, which together produce most of the skeleton of lovastatin in 35 highly programmed steps. We will study the step by step transformations of this remarkable molecular machine with the goal of elucidating its mechanism and generating new analogs of the drug. Similar approaches will be used to study biosynthesis of three other biologically active fungal polyketide compounds. A second part of the program targets bacteriocins, which are antimicrobial peptides produced by bacteria that occur naturally in food. They are many orders of magnitude more potent than conventional antibiotics and are effective against pathogens resistant to current therapy. In particular, chemical synthesis of lantibiotics, a class of bacteriocins that contain monosulfide lanthionine rings, will be investigated with the goal of understanding structure-activity relationships and making more stable derivatives. Targets include lacticin 3147 and gallidermin. Another aspect involves determination of the details of biosynthesis of thuricins, which are active against the dangerous pathogen, Clostridium difficile ribotype 027. Their the 3D structures will also be examined by new approaches