CEA Grenoble, Laboratoire de Biochimie et Biophysique des Systèmes Intégrés, UMR CEA/CNRS/UJF 5092, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), 17 rue des Martyrs, 38054 Grenoble cedex 9, France

摘要

The utilization of hydrogen by micro-organisms as a source of reducing power or of protons as final electron acceptors is mediated by metalloenzymes called hydrogenases. The need for catalytic transition metal centers is explained by the significant increase in the acidity of molecular hydrogen when bound to them.1 There are three phylogenetically unrelated classes of these enzymes: [NiFe]-and [FeFe]-hydrogenases, in which hydrogen is the only substrate or product, according to H2 <-> 2H+ + 2e-, and a third class in which hydrogen uptake is coupled to methenyltetrahydromethanopterin reduction.2 The latter is called FeS cluster-free hydrogenase because, as opposed to the other two enzymes, it lacks FeS cubane centers.3 Its active site contains a labile light-sensitive cofactor4 with a mononuclear low-spin iron, most likely Fe(II),5 that binds two CO ligands.6,7 The crystal structure of the apoenzyme was published in 2006,8 and more recently, the three-dimensional structure of the holoenzyme was reported at a Workshop on Biohydrogen, February 21-23, 2007, in Berlin, Germany (S. Shima et al., unpublished work). As we will discuss below, low-spin iron coordinated to CO is also present in [NiFe]- and [FeFe]-hydrogenases, indicating that a Fe(CO)x unit is central to biological hydrogen catalysis. Here, we will review [NiFe]- and [FeFe]-hydrogenases.