Hydrogenases Hydrolases

Nickel, Ni2+ (d8) 4, square planar S-Thiolate, thioether, V-i midazole, poly pyrrole Hydrogenases, hydrolases... 

The nickel enzymes covered in this article can be divided into two groups redox enzymes and hydrolases. The five Ni redox enzymes are hydrogenase, CO dehydrogenase (CODH), acetyl-CoA synthase (ACS), methyl-Coenzyme M reductase (MCR), and superoxide dismutase (SOD). Glyoxalase-I and urease are Ni hydrolases. Ni proteins that are not enzymes are not covered, because they have been recently reviewed. These include regulatory proteins (NikR) and chaperonins and metal uptake proteins (CooJ, CooE, UreE, and ABC transporters). A recent crystal structure of NikR, shown in Figure l(i), is a notable recent achievement in this area. ... 

Biological catalysis by Ni can be divided in two broad classes the hydrolase activity represented by urease and the redox-associated mechanisms typical of hydrogenase, S-methyl coenzyme M reductases and CODHs. 

Figure 7.12 Proposal pathway for PVA degradation by various enyme systems. 1) Pyrroloquinoline quinine (PQQ)-dependent PVA hydrogenase 2) oxidised PVA hydrolase 3) PVA-degrading enzyme with dehydrogenase and aldolase activities 4) secondary alcohol oxidase 5) p-diketone hydrolase and 6) PVA-degrading enzyme with oxidase and hydrolase activity. Reproduced with permission from M. Shimao, Current Opinion in Biotechnology, 2001, 12, 3, 242.

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