Enzymes catalase, bacterial

The effectors of the mammalian host immune attack against filaria include reactive oxygen intermediates. Filarial nematodes express glutathione peroxidase, thioredoxin peroxidase and superoxide dismutase at their surface - enzymes believed to protect the nematode from this attack (Selkirk et al., 1998). A bacterial catalase gene has been identified that most probably derives from the endosymbiont genome (Henkle-Duhrsen et al., 1998) this enzyme may contribute with other enzymes to the protection of both Wolbachia and its nematode host from oxygen radicals. 

Bacterial SODs typically contain either nonheme iron (FeSODs) or manganese (MnSODs) at their active sites, although bacterial copper/zinc and nickel SODs are also known (Imlay and Imlay 1996 Chung et al. 1999). Catalases are usually heme-containing enzymes that catalyze disproportionation of hydrogen peroxide to water and molecular oxygen (Eq. 10.2) (Zamocky and Koller 1999 Loewen et al. 2000). 

The maximum rate is directly related to the rate at which the enzyme processes or permits conversion of the reactant molecule(s). The number of moles of reactants processed per mole of enzyme per second is called the turnover number. Turnover numbers vary widely. Some are high, such as for the scavenging of harmful free radicals by catalase, with a turnover number of about 40 million. Others are small, such as the hydrolysis of bacterial cell walls by the enzyme lysozyme, with a turnover number of about one half. 

Although isoniazid has been in use for about 45 years, the enzyme that it inhibits has been recognized only recently. It is a specific NADH-depen-dent enoyl reductase involved in synthesis of mycolic acids.h/1 The isoniazid must be activated by action of a bacterial catalase-peroxidaseh This enzyme may convert the drug to a reactive radical that combines with a NADH-derived radical to form an adduct in the active site of the enzymes. One possible reaction sequence follows.11 However, the mechanisms are not clear. 

In fact, the a-ketoglutarate/glutamate dehydrogenase is a generally applicable method for the regeneration of NAD and NADP in laboratory scale productions. Both components involved are inexpensive and stable. Quite recently, a method for the oxidation of the reduced nicotinamide coenzymes based on bacterial NAD(P)H oxidase has been described [225], This enzyme oxidizes NADH as well as NADPH with low Km values. The product of this reaction is peroxide, which tends to deactivate enzymes, but it can be destroyed simultaneously by addition of catalase. The irreversible peroxide/catalase reaction favours the ADH catalyzed oxidation reaction, and complete conversions of this reaction type are described. 

Some of the basic information on stabilizing sulfhydryl enzymes, has been responsible for their commercialization. Without the judicious use of reducing compounds throughout the processing of the papaya latex, it would not have been possible to maximize the proteolytic activity of commercial papain preparations. Examples of other studies of enzymes which have contributed to commercialization are the determination of calcium ion as a requirement for amylase stability at high temperature, the difference in properties of catalases derived from bacterial, fungal, or... 

Purified enzymes were obtained from Sigma Chemicals catalase (E.C.1.11.1.6) and urease (E.C.3.5.1.5). They were immobilized on the fiber using g1utera 1dehyde (Fisher). Phosphate buffers (0.1 M> were used for fiber storage and as carriers in the FIA system. Thymol (50 mg/L) was used to inhibit bacterial and fungal growth in the buffer. 

If the Catalase Test indicates that the enzyme is present at significant or problematic concentrations, plate counts should be performed on stock samples prior to bleaching to determine the level of bacterial contamination. Toxicity studies can then be performed to select a biocide program that will control the bacteria. 

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