Oxidase enzymes bacterial

In the area of copper metabolism, four topics are covered bacterial copper transport reviewed by Huat Lu and Sohoz copper P-type ATPases reviewed by Voskoboinik, Camakaris, and Mercer copper chaperones reviewed by Stine Elam et al. and copper metaUoregulation of gene expression reviewed by Winge. An important related topic is the link between copper and iron metabolism. In this area, Kosman has reviewed the multicopper oxidase enzymes, such as FetSp and ceruloplasmin, which catalyze the conversion of iron(II) to iron(III) in preparation for its specific transport by partner transporter proteins. 

Covalent quinoproteins possess protein-derived cofactors derived from aromatic amino acid residues. These enzymes contain a posttranslationally modified tyrosine or tryptophan residue into which one or two oxygens has been incorporated (Figure 3). In some cases, the quinolated amino acid residue is also covalently cross-linked to another amino acid residue on the polypeptide. Tyrosine-derived quinone cofactors occur in oxidases from bacterial, mammalian, and plant sources. Tryptophan-derived quinone cofactors have been found thus far in bacterial dehydrogenases. 

A number of enzymes which catalyze oxidation reactions, including mammalian lysyl and plasma amine oxidases and bacterial alcohol dehydrogenases, have been determined to utilize pyrroloquinoline quinone (PQQ, methoxatin) as a cofactor (Duine et al., 1987). Substrates of the amine oxidases appear to be activated for a-proton abstraction by formation of a Schiff base with PQQ, fol-... 

Heme A is an obligatory cofactor in all eukaryotic and most bacterial cytochrome c oxidase enzymes (CcO). Because of its importance to CcO and aerobic metabolism, considerable effort has recently been invested in understanding the mechanism and regulation of heme A biosynthesis. The activity of heme A synthase is strictly dependent on O2, and yet there is no incorporation of O2 into the products. Heme A synthase is now known to utilize a unique electron-transfer mechanism when oxidizing heme O to heme A. Interestingly, the heme A biosynthetic pathway is regulated at least partly via a heme-dependent process in which heme A synthase is positively regulated by intracellular heme levels via Hapl. 

Chronic granulomatous disease results from an inability of phagocytic cells to produce bactericidal superoxide anions caused by a defect in the nicotinamide adenine dinucleotide phosphate (reduced form) oxidase enzyme of phagocytes. This leads to recurrent life-threatening bacterial and fungal infections. About two thirds of patients inherit... 

Bioerosion occurs without change in molar mass of the bulk polymer, confirming that the microbial attack is initially in the oxidation-modified polymer surface and progression into the polymer depends on the continuation of peroxidation catalysed by transition metal ions. The bacterial colonies also produce oxidase enzymes e.g. cytochrome P-450) which produce superoxide and hydrogen peroxide from oxygen of the environment. The latter in turn gives highly reactive hydroxyl... 

The active site geometries (Figure 2.14) of the sulfite oxidizing enzymes are quite similar and examples of high-resolution X-ray crystal structures can be found for the S. novella sulfite dehydrogenase (bacterial)/ A. thaliana sulfite oxidase (plant)/ bacterial YedY/ and vertebrate sulfite oxidase. ... 

The biochemical mechanism of bacterial luminescence has been studied in detail and reviewed by several authors (Hastings and Nealson, 1977 Ziegler and Baldwin, 1981 Lee et al., 1991 Baldwin and Ziegler, 1992 Tu and Mager, 1995). Bacterial luciferase catalyzes the oxidation of a long-chain aldehyde and FMNH2 with molecular oxygen, thus the enzyme can be viewed as a mixed function oxidase. The main steps of the luciferase-catalyzed luminescence are shown in Fig. 2.1. Many details of this scheme have been experimentally confirmed. 

Cytochrome enzymes, 2, 772 Cytochrome a3 oxidase, 6, 697 Cytochrome c oxidase, 6, 683 copper complexes, 2,724,772 Cytochrome oxidases, 6, 624 bacterial, 6,696... 

Tissue and Bacteria Electrodes The limited stability of isolated enzymes, and the fact that some enzymes are expensive or even unavailable in the pure state, has prompted the use of cellular materials (plant tissues, bacterial cells, etc.) as a source for enzymatic activity (35). For example, banana tissue (which is rich with polyphenol oxidase) can be incorporated by mixing within the carbon paste... 

Abramson J, Svensson-Ek M, Byrne B, Iwata S. 2001. Structure of cytochrome c oxidase A comparison of the bacterial and mitochondrial enzymes. Biochim Biophys Acta 1544 1. 

All amino acids except glycine exist in these two different isomeric forms but only the L isomers of the a-amino acids are found in proteins, although many D amino acids do occur naturally, for example in certain bacterial cell walls and polypeptide antibiotics. It is difficult to differentiate between the D and the L isomers by chemical methods and when it is necessary to resolve a racemic mixture, an isomer-specific enzyme provides a convenient way to degrade the unwanted isomer, leaving the other isomer intact. Similarly in a particular sample, one isomer may be determined in the presence of the other using an enzyme with a specificity for the isomer under investigation. The other isomer present will not act as a substrate for the enzyme and no enzymic activity will be demonstrated. The enzyme L-amino acid oxidase (EC 1.4.3.2), for example, is an enzyme that shows activity only with L amino acids and will not react with the D amino acids. 

For reactions in which one or more reactants or products is a gas, manometry (the measurement of pressure differences) can provide a convenient means for monitoring the course and kinetics of the reaction Thus, enzymes that can be assayed with this method include oxidases, urease, carbonic anhydrase, hydrogenase, and decarboxylases. For example, bacterial glutamate decarboxylase is readily assayed by utilizing a Warburg flask and measuring the volume of gas evolved at different times using a constant-pressure respirometer. ... 

Putidaredoxin. Cushman et al. (36) isolated a low molecular iron-sulfur protein from camphor-grown Pseudomonas putida. This protein, putidaredoxin, is similar to the plant type ferredoxins with two irons attached to two acid-labile sulfur atoms (37). It has a molecular weight of 12,000 and shows absorption maxima at 327, 425 and 455 nm. Putidaredoxin functions as an electron transfer component of a methylene hydroxylase system involved in camphor hydroxylation by P. putida. This enzyme system consists of putidaredoxin, flavoprotein and cytochrome P.cQ (38). The electron transport from flavoprotein to cytochrome P.cq is Smilar to that of the mammalian mixed-function oxidase, but requires NADH as a primary electron donor as shown in Fig. 4. In this bacterial mixed-function oxidase system, reduced putidaredoxin donates an electron to substrate-bound cytochrome P. g, and the reduced cytochrome P. g binds to molecular oxygen. One oxygen atom is then used for substrate oxidation, and the other one is reduced to water (39, 40). 

Megaredoxin. Another example of a bacterial mixed-function oxidase was found in the steroid 15 6-hydroxylase system of Bacillus megaterium (41). This enzyme system consists of three proteins FMN-containing flavoprotein (megaredoxin reductase), iron-sulfur protein... 

Complex IV Cytochrome c to 02 In the final step of the respiratory chain, Complex IV, also called cytochrome oxidase, carries electrons from cytochrome c to molecular oxygen, reducing it to H20. Complex IV is a large enzyme (13 subunits Mr 204,000) of the inner mitochondrial membrane. Bacteria contain a form that is much simpler, with only three or four subunits, but still capable of catalyzing both electron transfer and proton pumping. Comparison of the mitochondrial and bacterial complexes suggests that three subunits are critical to the function (Fig. 19-13). 

Microsomal activation for bacterial assays typically has involved crude supernatant fractions (S9) from livers of rats induced by polychlorobiphenyl mixtures, usually Aroclor 1254. These S9 mixtures contain a spectrum of mixed function oxidases and other enzymes active in biotransformation. In such mixtures, a given compound might be activated to become more mutagenic, may be inactivated, or may remain unaffected. All three types of response have been observed with various water residues (9, 14). 

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