ENZYMES OF PURINE SALVAGE

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 嘌呤是许多细胞过程的必需分子，包括核酸和核苷酸代谢、能量转移和储存、蛋白质合成和信号传导。 此外，当氨不存在或限制时，一些生物体可以利用嘌呤作为氮源。 嘌呤催化的第一步是腺嘌呤或鸟嘌呤分别脱氨基为次黄嘌呤或黄嘌呤。 剩下的分解代谢步骤可以分为两部分。 第一个是所有物种共有的，是通过一系列酶将（次）黄嘌呤分解为尿囊素。 该途径的第二部分，即尿囊素降解为CO2和氨，可能因微生物物种而异。 最近，在肺炎克雷伯氏菌中鉴定了一组负责次黄嘌呤氧化为尿囊素的七个基因。 另一个研究小组的进一步工作确定了参与这一途径的另外五个基因，包括鸟嘌呤脱氨酶和负责将尿囊素转化为尿囊酸的酶。 这两个小组的工作还表明，K。肺炎克雷伯氏菌与大多数报道的黄嘌呤氧化酶或氧化还原酶不同，其独立于含钼酶而存在。 我们已经开始了几个酶的结构研究，负责次黄嘌呤在K。肺炎。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Purines are essential molecules for many cellular processes including nucleic acid and nucleotide metabolism, energy transfer and storage, protein synthesis and signaling. In addition, some organisms can utilize purines as a nitrogen source when ammonia is absent or limiting. The first step of purine catabolism is a deamination of adenine or guanine to hypoxanthine or xanthine respectively. The remaining catabolic steps can be divided into two parts. The first, common to all species, is the breakdown of (hypo)xanthine to allantoin over several steps by a series of enzymes. The second part of the pathway, the degradation of allantoin to CO2 and ammonia, can vary between microbial species. Recently a set of seven genes responsible for the oxidation of hypoxanthine to allantoin in Klebsiella pneumoniae has been identified. Further work by a different group identified an additional five genes involved in this pathway, including the guanine deaminase and enzymes responsible for the conversion of allantoin to allantoate. The work by these two groups also demonstrated that the cofactors required for the breakdown of xanthine in K. pneumoniae differs from most of the reported xanthine dehydrogenases or oxidoreductases, occurring independently of molybdenum containing enzymes. We have initiated structural studies of several of the enzymes responsible for the catabolism of hypoxanthine in K. pneumoniae.