Other Mononuclear Zinc Enzymes

FIGURE 12.9 Reactions catalysed by SDR enzymes. (Adapted from Kavanagh, drnvall, Persson, i4 Oppermann, 2008.) 

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Figure 12.8 Some other active-site coordination motifs in mononuclear zinc enzymes from left to right bacteriophage T7 lysozyme, 5-aminolaevulinate dehydratase, Ada DNA repair protein. (Reprinted with permission from Parkin, 2004. Copyright (2004) American Chemical Society.)...

We consider, successively, the catalytic role of several classes of mononuclear Zn2+ enzymes and then discuss enzymes with di- and tri-nuclear cocatalytic zinc centres, some of which include a metal ion other than zinc. We conclude with a presentation of some of the zinc-based motifs found in proteins involved in the regulation of nucleic acid and protein synthesis. 

There are several additional examples of zinc enzymes that contain an active site mononuclear zinc center and catalyze the hydrolysis of peptides bonds. These include carboxypeptidase B83 and neutral protease84 both of which contain a [(NHis)2(OGiu/AsP)Zn-OH2] coordination motif within the enzyme active site. Zinc peptidases that contain a [(NHis)3Zn-OH2] active site metal center include matrix metalloproteinases85,86 and other members of the metzincins superfamily.77,85... 

There are two distinct forms of MMOs one is soluble MMO (sMMO), which contains a nonheme dinuclear iron center, and the other is particulate MMO (pMMO), which is a copper-containing enzyme. Although sMMO has been well characterized and studied (78,79), many aspects of pMMO chemistry and biochemistry remain unclear. Because of the difficulty in the isolation and purification of pMMO, four different research groups have reported various ranges of copper stoichiometries for purified pMMO 2 (80), 2-3 (81) 8-10 (82), and 15-20 (83) copper ions per 100 kDa. The first crystal structure of pMMO firom M. capsulatus Bath (28) shows a heterotrimer of three subunits, and each subunit contains three polypeptides pmoB (a, 47 kDa), pmoA (, 24 kDa), and pmoC (y, 22 kDa). Three types of metal centers were found in pMMO a mononuclear copper, a dinuclear copper center in pmoB, and a zinc center in pmoC. 

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