Pseudomonas peroxidase

Furthermore, the preparation of the antibiotic Pyrrolnitrine by oxidation of the amino-functionalized precursor with the chloroperoxidase from Pseudomonas pyrrocinia was reported (Eq. 13) [155]. The mechanism of this peroxidase-catalyzed N-oxidation has not been elucidated. 

Such an involvement of an amino acid side-chain ligand switch within each catalytic cycle was a novel proposal and as such needs to be scrutinized by a variety of experimental procedures as well as analysis in the context of information known for cytochrome cd nitrite reductase from another source (see later discussion). However, it is interesting to note that something similar has been proposed for the protocate-chuate 3,4-dioxygenase enzyme from Pseudomonas putida (15). On the other hand, bacterial cytochrome c peroxidase offers an example where ligand switching seemingly relates only to an activation phenomenon. 

It is nearly 50 years since a c-type cytochrome was shown to catalyze peroxidase activity in crude extracts of Pseudomonas fluorescens (40). The enzyme responsible was first purified some 20 years later by Ell-folk and Soninen from the closely related P. aeruginosa and shown to be a diheme cytochrome c peroxidase (CCP) (41). These bacterial diheme CCPs are quite distinct from the superfamily of plant and yeast peroxidases (42) and are widely distributed among the Gram-negative bacteria (41, 43 6). Diheme CCPs are located in the periplasm (Fig. 2), where they catalyze the two-electron reduction of H2O2 to H2O by soluble one-electron donors such as cytochromes c and cupredoxins. 

B. Structure of Cytochrome c Peroxidase from Pseudomonas aeruginosa... 

Pseudomonas aerogenes ferredoxin, 33 55-56 Pseudomonas aeruginosa bacfer iron cores, 36 452 diheme cytochrome c peroxidase, 36 242-245... 

Hoft reported about the kinetic resolution of THPO (16b) by acylation catalyzed by different lipases (equation 12) °. Using lipases from Pseudomonas fluorescens, only low ee values were obtained even at high conversions of the hydroperoxide (best result after 96 hours with lipase PS conversion of 83% and ee of 37%). Better results were achieved by the same authors using pancreatin as a catalyst. With this lipase an ee of 96% could be obtained but only at high conversions (85%), so that the enantiomerically enriched (5 )-16b was isolated in poor yields (<20%). Unfortunately, this procedure was limited to secondary hydroperoxides. With tertiary 1-methyl-1-phenylpropyl hydroperoxide (17a) or 1-cyclohexyl-1-phenylethyl hydroperoxide (17b) no reaction was observed. The kinetic resolution of racemic hydroperoxides can also be achieved by chloroperoxidase (CPO) or Coprinus peroxidase (CiP) catalyzed enantioselective sulfoxidation of prochiral sulfides 22 with a racemic mixmre of chiral hydroperoxides. In 1992, Wong and coworkers and later Hoft and coworkers in 1995 ° investigated the CPO-catalyzed sulfoxidation with several chiral racemic hydroperoxides while the CiP-catalyzed kinetic resolution of phenylethyl hydroperoxide 16a was reported by Adam and coworkers (equation 13). The results are summarized in Table 4. 

Cytochrome c peroxidase may also be isolated from Pseudomonas spp. and differs from the yeast enzyme described above. Pseudomonas cytochrome c peroxidase contains two covalently bound heme c moieties in a single polypeptide chain, of molecular weight 50 000. The enzyme from Ps. denitrificans has a molecular weight of 63 000 with two heme c groups.1370... 

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... 

Other peroxidases, albeit non-heme, are able to catalyze similar oxidations. CPO from Pseudomonas pyrrocinia has been successfully employed for the preparation of the antibiotic pyrrolnitrine [60]. The amino group of the precursor molecule is directly transformed into a nitro group by the CPO active species (Fig. 6.4b). 

Dihaem cytochrome c peroxidase (Pseudomonas aeruginosa) haem B (His) None 3.1.1.1. 

Finally, as usual, bacteria provide an exception to the general rule. In this case the di-haem cytochrome c peroxidase from Pseudomonas aeruginosa removes its electron, not from a porphyrin, nor an amino acid, but instead from a separate high-potential haem, which is converted from Fe11 to Fe111 [22]. This proves that, at least for peroxidases, nature can manage very well without protein-bound free radicals if necessary. 

Fig. 8. MCD spectra of ferryl iron. Low-temperature (50 or 100K) MCD spectra of ferryl iron in different proteins HRPCII, horse-radish peroxidase compound II HRPCX, horse-radish peroxidase compound X YCCP, yeast cytochrome c peroxidase compound I PsCCP, compound I of the dihaem cytochrome c peroxidase from Pseudomonas aeruginosa-, Mb pH 3.5, ferryl myoglobin formed at pH 3.5 MbpD9.0, the same compound found at pD9.0. Note the similarity of all the spectra with the exception of the alkaline form of ferryl myoglobin. Reprinted with permission from Cheesman, M.R., Greenwood, C. and Thomson, A.J. (1991) Adv. Inorg. Chem. 36, 201-255.

MCD spectra perhaps provide the best fingerprint for the existence of an FeIV=0 structure. Fig. 8 shows that there is a great similarity between the spectra of horseradish peroxidase compound II, horseradish peroxidase compound X, cytochrome c peroxidase compound I, Pseudomonas aeruginosa peroxidase compound I and ferryl myoglobin at acid pH. Similar features are seen in the spectra of catalase [170] and myoglobin [171] compound II. 

Figure 7 Schematic representation of the of di-heme peroxidases from Pseudomonas aeruginosa (PAP) and Nitrosomonas europea (NEP) showing key residues involved in catalysis. (This figure was generated from coordinates of 1EB7 and IIQC deposited in the Protein Data Bank)...

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. 

C. Diheme Cytochrome c Peroxidase Pseudomonas aeruginosa) Metal Centers of Cytochrome c Oxidase... 

There is a third class of peroxidases isolable from the bacterial sources such as P. aeruginosa and Pseudomonas stutzerii, which oxidize cytochrome C551, or azurin. This protein contains two heme protoporphyrin IX groups covalently bound to a single polypeptide side chain. In this enzyme one heme group is oxidized from Fe(III) to Fe(IV)=0 and the second heme, from Fe(II) to Fe(III). The oxidizing equivalents are directed to two centers with very different redox potentials (75). 

There is good evidence to show that the two hemes in Pseudomonas cytochrome c peroxidase are not equivalent. One is a c type heme (+320 mV), and the other is a c heme (—330 mV) and is a peroxidatic group. A number of techniques, including CD, absorption and resonance Raman spectroscopy, show that the fifth ligand in both hemes is an imidazole group. In the oxidized... 

Hydroxytryptophan was not metabolized by a tryptophan-adapted strain of Pseudomonas (217) and was not attacked by the tryptophan peroxidase-oxidase system (217, 884). The enteramine and kynurenine pathways are quite distinct, as is supported by the facts that synthetic 5-hydroxykynurenine (124, 574), the expected product of tryptophan peroxidase-oxidase action, does not act as an ommochrome precursor in insects or as a nicotinic acid precursor in Neurospora (124). 

ILs have been used for immobilization of enzymes. Horseradish peroxidase (HRP) activity is evaluated in a [BMIM][BF ] sol-gel matrix [26]. Higher activity in [BMIM][PFg] is also observed when lipase from an unspecified Pseudomonas (PsL) is immobilized on methacryloxypropyl-modified mesoporous silica [27]. Similarly, IL-coated enzyme was found to completely retain the activity and easily reusable [28]. 

Bromoperoxidase has been isolated from Pseudomonas aureofaciens ATCC 15926, also displays peroxidase and catalase activities, and contains ferriprotoporphyrin IX (van Pee and Lingens 1985). Four different bromoperoxidases have been isolated from Streptomyces griseus (Zeiner et al. 1988). Only one of them, however, contains ferriprotoporphyrin IX and displays peroxidase and catalase activities. This illustrates that there are two different groups of enzymes, one of which lacks heme prosthetic groups. 

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