Microbial reductases

The second major type of reductive metabolism of anthracyclines is the reduction of 13-0X0 anthracyclines to their 15-dihydro analogs (182,183,244,287-293). This keto reduction reaction at Cl3 appears to be carried out by a wide variety of microbial reductases with broad or low substrate specificity (184,244,287-293). In a potential application of this reductive reaction, Marek et al. (291) demonstrated that immobilized mycelia of Strepltmiycej awreo/ociens strain B-96 can reduce daunonibtcinone to 13-dihydrodaunoru-bicinone. 

The general mechanism of nitrosation of secondary amines is shown in Figure 12.26. Nitrosation reagents are formed in acidic solutions from nitrous acid and nitrites, respectively, by a sequence of reactions indicated in Figure 12.27. Nitrites are present in foods as additives or contaminants. In foods and beverages obtained by fermentation, nitrites may arise by reduction of nitrates by microbial reductases. In beer, for example, wild yeasts partly assimilate nitrates to give ammonia, and the activity of nitrate reductase... 

The reduction of C=C bonds has been conducted with catalysis by plant and microbial reductases. Scheme 33.17 summarized the enantioselective reduction of olefins by plant and microalgae. The stereoselective reduction of 2-butenolides was conducted by two... 

The sulfa dmgs are stiH important as antimicrobials, although they have been replaced in many systemic infections by the natural and semisynthetic antibiotics. They are of great value in third world countries where problems of storage and lack of medical personnel make appropriate use of antibiotics difficult. They are especially useful in urinary tract infections, particularly the combination of sulfamethoxazole with trimethoprim. Their effectiveness has been enhanced by co-adniinistration with dihydrofolate reductase inhibitors, and the combination of sulfamethoxazole with trimethoprim is of value in treatment of a number of specific microbial infections. The introduction of this combination (cotrimoxazole) in the late 1960s (1973 in the United States) resulted in increased use of sulfonamides. 

McEwan AG, IP Ridge, CA McDevitt, P Hugenholtz (2002) The DMSO reductase family of microbial molybdenum enzymes molecular properties and the role in the dissimilatory reduction of toxic elements. 

The po.ssible role of a chelate reductase for iron uptake from microbial siderophores has been examined for several plant species (30,47). With certain microbial siderophores such as rhizoferrin and rhodotorulic acid, the reductase may easily cleave iron from the siderophore to allow subsequent uptake by the ferrous iron transporter. However, with the hydroxamate siderophore, ferrioxamine B, which is produced by actinomycetes and u.sed by diverse bacteria and fungi, it has been shown that the iron stress-regulated reductase is not capable... 

Kataoka, M., Hoshino-Hasegawa, A., Thiwthong, R. et al. (2006) Gene cloning of an NADPH-dependent menadione reductase from Candidamacedoniensis, and its application to chiral alcohol production. Enzyme and Microbial Technology, 38 (7), 944—951. 

Based on the previous publications, azo dye can be reduced by azoreductase-catalyzed reduction under anaerobic conditions. But still there is a speculation whether bacterial flavin reductases are responsible for the azo reductase activity observed with bacterial cell extracts. In a published report, it is reported that flavin reductases are indeed able to act as azo reductases [24]. Bacteria produce extracellular oxidative enzymes, which are relatively nonspecific enzymes catalyzing the oxidation of a variety of dyes. It was reported that so many diverse groups of bacteria play a role in decolorization. It has been also reported that mixed microbial community could reduce various azo dyes, and members of the y-proteabacteria and sulfate reducing bacteria (SRB) were found to be prominent members of mixed bacterial population by using molecular methods to determine the microbial population dynamics [1],... 

Recently, a new polyketide biosynthetic pathway in bacteria that parallels the well studied plant PKSs has been discovered that can assemble small aromatic metabolites.8,9 These type III PKSs10 are members of the chalcone synthase (CHS) and stilbene synthase (STS) family of PKSs previously thought to be restricted to plants.11 The best studied type III PKS is CHS. Physiologically, CHS catalyzes the biosynthesis of 4,2, 4, 6 -tetrahydroxychalcone (chalcone). Moreover, in some organisms CHS works in concert with chalcone reductase (CHR) to produce 4,2 ,4 -trihydroxychalcone (deoxychalcone) (Fig. 12.1). Both natural products constitute plant secondary metabolites that are used as precursors for the biosynthesis of anthocyanin pigments, anti-microbial phytoalexins, and chemical inducers of Rhizobium nodulation genes.12... 

Although mammalian CYPs are attractive candidates for use as commercial biocatalysts, many functional characteristics limit the opportunities to exploit such a system. Association of the enzymes with membranes prevents easy extraction and purification and limits the opportunities to produce useful recombinant enzymes by cloning the relevant genes for expression in microbial systems. All P450s have a porphyrin-haem active site that requires a second protein to reduce the iron component, often cytochrome P450 reductase or... 

Rosuvastatin calcium (56 Crestor ) Mevastatin Statin NP-derived Microbial Dyslipidemia Inhibits ttie rate-limiting step in hie formation of endogenous cholesterol by HMG-CoA reductase 215-217, 492-495... 

The biological functions of chloroplast ferredoxins are to mediate electron transport in the photosynthetic reaction. These ferredoxins receive electrons from light-excited chlorophyll, and reduce NADP in the presence of ferredoxin-NADPH reductase (23). Another function of chloroplast ferredoxins is the formation oT" ATP in oxygen-evolving noncyclic photophosphorylation (24). With respect to the photoreduction of NADP, it is known that microbial ferredoxins from C. pasteurianum (16) are capable of replacing the spinach ferredoxin, indicating the functional similarities of ferredoxins from completely different sources. The functions of chloroplast ferredoxins in photosynthesis and the properties of these ferredoxin proteins have been reviewed in detail by Orme-Johnson (2), Buchanan and Arnon (3), Bishop (25), and Yocum et al. ( ). 

As has been described in a recent review of low-molecul2u -welght enzyme inhibitors of microbial origin (65), hypotensive coo unds, ccmipounds useful in the treatment of diabetes or obesity, and con unds useful in the treatment of hypercholestremla have been discovered by the screening for inhibitors of catecholamine-synthesizing enzymes, amylase, or 3-hydroxy-3 metl lglu-taryl coenzyme A reductase respectively. 

Diketone and Other Ketone Reductases from Microbial Sources... 

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