Heme peroxidases crystal structures

Most well-studied peroxidases are designed to oxidize small aromatic molecules, with the exception of cytochrome c peroxidase. It generally is thought that such aromatic molecules bind near the heme edge where an electron can transfer directly to the heme edge (44), which is supported by both crystal structures (45, 46) and NMR studies (47). However, recent work suggests that some physiologically important substrates may utilize other sites on the enzyme surface (48, 49). 

Jin S, Kurtz DM, Liu ZJ, Rose J, Wang BC (2002) X-ray crystal structures of reduced rubr-erythrin and its azide adduct a structure-based mechanism for a non-heme diiron peroxidase. J Am Chem Soc 124 9845-9855... 

Sundaramoorthy M, Temer J, Poulos TL (1995) The Crystal Structure of Chloroperoxidase A Heme Peroxidase-Cytochrome P450 Functional Hybrid. Structure 3 1367... 

New insights into the peroxide binding and in the catalysis, obtained through site-directed mutagenesis, have led to much-improved understanding of heme peroxidases and their possible applications. New crystal structures of peroxidases have provided much more information on the local heme environments [32],... 

Figure 1. (a) X-ray crystal structure of horse-heart ferricytochrome c.8 All protein atoms are shown in the C.-P.-K. form, while the heme group is shown in the stick form. All Arg and Lys residues are colored blue, while Glu and Asp are colored in red, to contrast the destribution of the most ionizable side chains, (b) The X-ray crystal structure of horse heart ferricytochrome c in complex with horse cytochrome c peroxidase (cep).9 The peroxidase is shown as a molecular surface model, with blue regions depicting positive and red representing negative electrostatic potential. Note the cluster of negative potential on ccp that surrounds the contact interface. 

The superfamily of plant, fungal, and bacterial heme peroxidases (also called non animal peroxidase superfamily, see Chap. 2) categorizes its components into three classes based on sequence alignment and biological origin, such as initially proposed by K.G. Welinder using the only crystal structure available at that moment (yeast CCP) as a model [3, 4]. Class III is the largest one, with over 3,000 plant peroxidase entries in PeroxiBase, followed by Classes I and II, with over 900 entries... 

Fig. 3.2 Solvent access surface (colors represent electrostatic potentials) showing the main channel providing access to the heme cofactor (in yellow bars) occupying a central cavity (heme pocket) and the second narrow channel present in some peroxidases, such as manganese-oxidizing peroxidases, accessing to the heme propionates (based on the crystal structure of P. eryngii VP, PDB 2BOQ)...

Although CPO was first describe in 1966 [85] it was not until 1995 that its crystal structure was solved [27]. The crystal structure of the novel heme-thiolate aromatic -peroxygenase from A. aegerita has not been yet published, therefore, the CPO molecular structure is described herein as representative for the heme-thiolate peroxidases. 

Fiilop V, Ridout CJ, Greenwood C et al (1995) Crystal-structure of the di-heme cytochrome-c peroxidase from Pseudomonas aeruginosa. Structure 3 1225-1233... 

Zubieta C, Krishna SS, Kapoor M et al (2007) Crystal structures of two novel dye-decolorizing peroxidases reveal a beta-barrel fold with a conserved heme-binding motif. Proteins 69 223-233... 

A H-bonded triad Hisl 18-Asp237-Trp48 (Figures 4 and 5A) between the diiron centre of R2 and the surface of the protein was recognised already in the initial report of the crystal structure of R2 (Nordlund et al., 1990). It mimicked a His-Asp-Trp triad in cytochrome c peroxidase (Edwards et al., 1988) that connects the metal ion of the heme group with a tryptophan residue known to harbour a transient radical (Huyett et al., 1995). 

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