ON THE MECHANISM OF [NIFE]-HYDROGENASES

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目及 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 中心，但不一定是研究者所在的机构。 大自然利用分子氢作为能源的方法是基于自己的一套催化剂。其中两个被称为[FeFe]和[NiFe]氢化酶含有双核金属核心作为催化位点，而第三个被称为[Fe]氢化酶起源于单核。虽然这些酶的主要结构特征已经从蛋白质晶体学研究中获得，但与生物氢产生或消耗相关的催化机制的重要细节仍然未知。这种信息的缺乏是由于一个特殊的问题：X射线晶体学对这些酶的底物几乎是盲目的，例如，如果氢原子与金属原子配位或位于它们的直接相邻位置，则氢原子。另一个缺乏迫切需要的信息与[NiFe]氢化酶，这是孤立的氧化未准备阶段。在Ni-B阶段的情况下，羟基或氧代配体已被确定为连接Ni和Fe的第三桥，但由于酶的氧化损伤，采用Ni-A阶段的酶内的确切桥接情况仍然是有争议的辩论的主题。这种损伤导致不同改性物质的叠加，其中之一被提议为不能明确解决的过氧化氢或过氧化桥系统。

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. Natures approach towards utilizing molecular hydrogen as an energy source is based on an own set of catalysts. Two of them which are termed as [FeFe] and [NiFe] hydrogenases contain binuclear metal cores as catalytic sites, whereas the third one termed [Fe] hydrogenase is mononuclear in origin. Though principal structural features of these enzymes have been obtained from protein crystallographic investigations important details of the catalytic mechanisms associated with biological hydrogen production or consumption are still not known. This lack of information is due to a particular problem: X-ray crystallography is practically blind for the substrate of these enzymes, e.g. for hydrogen atoms if they are coordinated to metal atoms or situated in their direct neighborship. Another lack of urgently needed information is associated with the [NiFe] hydrogenases which are isolated in oxidized unready stages. In the case of the Ni-B stage, a hydroxo or oxo ligand has been identified as a third bridge connecting Ni and Fe, but the exact bridging situation within the enzyme adopting the Ni-A stage is still the subject of a controversial debate due to oxidation damage of the enzyme. This damage results in a superposition of differently modified species, one of which is proposed as a hydroperoxo or peroxo bridge system which cannot be resolved unambiguously.