Mammalian peroxidases superfamilies

G. Plant and Mammalian Peroxidase Superfamilies Mechanisms of Compound I Formation Endogenous Reduction of Peroxidase Intermediates Exogenous Reduction of Peroxidase Intermediates... 

Mammalian peroxidases. Mammalian peroxidases [19] make up a separate peroxidase superfamily (not homologous to any of the enzymes in the previous section). They include proteins used for defence, such as myeloperoxidase [33], lactoperoxidase [34], salivary peroxidase [35] and eosinophil peroxidase [36], as well as those used for biosynthesis, such as thyroid peroxidase [37]. All these enzymes can oxidise halides and pseudohalides in vitro, the main difference being in the redox potential of compound I [38],... 

Peroxidases fall into two superfamilies (plant and mammalian) and a third, indistinct group that includes chloroperoxidase (a P450-like hybrid) and di-heme cytochrome c peroxidase from Pseudomonas aeruginosa. The plant peroxidase superfamily contains enzymes of plant, fungal, and bacterial origin [126], Mammalian peroxidases make up the second superfamily, and include lactoperoxidase, myeloperoxidase, and prostaglandin H synthase. Both families have been the focus of numerous excellent reviews, several of which have discussed the differences between the plant and mammalian peroxidases [126-130], Here, recent experimental investigations focused on the plant peroxidases will be discussed. 

As with the plant peroxidase superfamily and other families of homologous enzymes 27, 28), it is to be anticipated that the 3D structures of the mammalian peroxidases will be shown to be very similar. A comparison of the sequences of MPO, TPO, EPO, and LPO reveals that the residues surrounding the heme are highly conserved (7, 14), suggesting a common heme environment for these four mammalian peroxidases. Furthermore, all 12 cysteines involved in the six disulfide bridges in MPO (Fig. 7) are conserved in the four mammalian peroxidases. Thus, if the pattern of disulfide bonds seen in MPO is also conserved, the 3D structures are likely to be very similar 14). 

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