BIOSYNTHESIS OF ARA-A, 2'-DEOXYCOFORMYCIN AND ANALOGUES

此续订提案是协作的拟议延续 大卫·贝克教授的实验室与 罗伯特·J·苏哈多尔尼克教授解释生物合成途径 一类具有重要药用价值的核苷类化合物，包括Ara-A和2‘- 脱氧考福霉素(2‘-DCF)。前者是一种临床上有用的抗病毒药物 (抗疱疹药物)，后者是腺苷的有效抑制剂 脱氨酶，最近被发现在临床上有用处 毛细胞白血病的治疗。当前提案的目标是 (1)总结我们对Ara-A生物合成的研究 腺苷2‘-异构化的机制，目前 假定为自由基过程或涉及NAD的过程 在氧化还原过程中。腺苷2‘-酶的详细研究 同向异构酶，包括用光亲和力探测其活性部位 这种酶的标记和基因克隆正在计划中。(2) 阐明腺苷转化为2‘-DCF的确切途径。 概述了生物合成中的中间体将被 通过现代光谱方法进行分离和充分表征，具有 用稳定同位素标记的化合物的辅助。这类研究 将有助于阐明2‘-DCF中其他核苷的途径 家系，包括2‘-氯-2’-脱氧考福霉素和考福霉素。 这些类似物之间的生物合成途径的相互关系将 有洞察力。CF氯化合成2‘-CldCF的反应机理 要下定决心。这种酶，8-酮-2‘-DCF还原酶，能还原8-酮-2’-DCF还原酶。 将详细研究酮基脱氧代福霉素制2‘-DCF，目的是 用光亲和标记物探测活性部位并克隆基因 将这种酶转化为变铅青链霉菌。后者被认为是 通过目前可用的化学品生产2‘-DCF的可能用途 涉及8-酮-2‘-DCF的非特异性还原的合成。 (3)阐明了一组相关化合物的生物合成 包括环戊烯醇，2‘-DCF的环戊烯类似物；阿奇霉素，a 1，4-二氮杂卓；以及含氟糖的核苷--杀核素。

This renewal proposal is a proposed continuation of the collaborative efforts between the laboratory of Prof. David C. Baker and that the Prof. Robert J. Suhadolnik to elucidate the biosynthetic pathways to a group of medicinally important nucleosides, which includes ara-A and 2'- deoxycoformycin (2'-dCF). The former is a clinically useful antiviral (antiherpes agent), and the latter is a potent inhibitor of adenosine deaminase that has recently been found to be of clinical utility in the treatment of hairy-cell leukemia. Goals of the current proposal are to (1) Conclude our studies on the biosynthesis of ara-A by defining the mechanism for the 2'-epimerization of adenosine, which is currently postulated to be either a free-radical process or one which involves NAD in a redox process. Detailed studies on the enzyme, adenosine 2'- epimerase, including the probing of its active site with photoaffinity labels and the cloning of the gene for the enzyme, are planned. (2) Elucidate the precise pathway by which adenosine is converted to 2'-dCF. Plans are outlined whereby intermediates in the biosynthesis will be isolated and fully characterized via modern spectroscopic methods, with the assistance of compounds labeled with stable isotopes. Such studies will serve to elucidate the pathways to other nucleosides in the 2'-dCF family, including 2'-chloro-2'-deoxycoformycin and coformycin. Interrelationships in the biosynthetic pathways among these analogues will be discerned. The mechanism for chlorination of CF to give 2'-CldCF will be determined. The enzyme, 8-keto-2'-dCF reductase, which reduces 8- ketodeoxycoformycin to 2'-dCF will be studied in detail, with the aim of probing the active site with photoaffinity labels and cloning the gene for producing the enzyme into S. lividans. The latter is considered of possible utility in producing 2'-dCF via the currently available chemical synthesis which involves a nonspecific reduction of the 8-keto-2'-dCF. (3) Elucidate the biosynthesis of a group of related compounds which includes adecypenol, a cyclopentenyl analogue of 2'-dCF; azepinomycin, a 1,4-diazepine; and nucleocidin, a fluorosugar-containing nucleoside.