Activity reductase

FIGURE 25.33 HMG-CoA reductase activity is modulated by a cycle of phosphorylation and dephosphorylation. 

TABLE 9. Comparison of Met(0)-peptide reductase activity in normal and cataractous lens... 

Another example for the use of hydrogen as reductant is observed in the reduction of imine [5b]. New imine reductase activity has been discovered in the anaerobic bacterium Acetobacterium woodii by screening a dynamic combinatorial library of virtual imine substrates, using a biphasic water-tetradecane solvent system. 

For example, a screening of 416 strains (71 bacterial strains, 45 actinomycetes, 59 yeast, 60 basidiomycetes, 33 marine fungi, and 148 filamentous fungi) has been performed to look for microorganisms that display reductase activity in the absence of oxidase activity [8b]. A new microorganism, Diplogdasinospora grovesii IMI... 

Mariotti, A., Mariotti, F., Champigny, M.L., Amarger, N. and Moyse, A. 1982 Nitrogen isotope fractionation associated with nitrate reductase activity and uptake of NO3by pearl millet. Plant Physiology 69 880-884. 

Considering the example of drought-induced increase in monodehydroa-scorbate reductase activity (Fig. 8) and assuming the increased activity reflects increased synthesis, isolation of the corresponding genes via the cDNA route should give us access to another set of stress-inducible... 

Fig. 8. The relationship between leaf water potential (V>l) mono-dehydroascorbate reductase activity in barley leaves during a 7-day drying period, r = 0.72, P<0.001 (from Smirnoff Colombe, 1988).

WALLiGM A, KINGSTON s, STAACK R and JEFFEREY E H (1998) Induction of rat pancreatic glutathione S-transferase and qitinone reductase activities by a mixture of glucosinolate breakdown derivatives foimd in Brussels sprouts . Food Chem Toxicol, 36 365-73. 

Eschenbrenner M, E Coves, M Fontecave (1995) The flavin reductase activity of the flavoprotein component of sulfite reductase bom Escherichia coli. J Biol Chem 270 20550-20555. 

Reductase activity is located on the outer membranes of Shewanella putrefaciens and has a requirement for cytochrome c (Myers and Myers 1997) and menaquinones (Saffarini et al. 2002). 

Wang P, T Mori, K Toda, H Ohtake (1990) Membrane-associated chromate reductase activity from Enterobacter cloacae. J Bacterial 172 1670-1672. 

Steingrube VA, RJ Wallace, LC Steele, Y Pang (1991) Mercuric reductase activity and evidence of broad-spectrum mercury resistance among clinical isolates of rapidly growing mycobacteria. Antimicrob Agents Chemother 35 819-823. 

This pathway is supported by the demonstration of benzyl alcohol dehydrogenase, benzaldehyde dehydrogenase, benzoyl-CoA ligase, and benzoyl-CoA reductase activities in cell extracts (Biegert and Fuchs 1995). The benzyl alcohol dehydrogenase from benzyl alcohol-grown cells was similar in many of its properties to those from the aerobic bacteria Acinetobacter calcoaceticus and Pseudomonas putida (Biegert et al. 1995). 

M. J. Holden, D. G. Luster, R. L. Chaney, T. J. Buckhout. and C. Robinson, Fc -chelate reductase activity of plasma membranes isolated from tomato (Lyco-persicon escidentiim Mill.) roots. Comparison of enzymes from Fe-deficient and Fe-sufficient roots. Plant Physiol. 97 531 (1991). 

M. A. Adams and P. M. Attiwill, Nitrate reductase activity and growth response of forest species to ammonium and nitrate sources of nitrogen. Plant Soil 66 373 (1982). 

Resins are moderately effective in lowering LDL cholesterol but do not lower triglycerides (Table 9-8). Moreover, in patients with elevated triglycerides, the use of a resin may worsen the condition. This may be due to a compensatory increase in HMG-CoA reductase activity and results in an increase in assembly and secretion of VLDL. The increase in HMG-CoA reductase activity can be blocked with a statin, resulting in enhanced reductions in serum lipids (see section on combination therapy). Resins reduce LDL cholesterol from 15% to 30%, with a modest increase in HDL cholesterol (3% to 5%) (Table 9-8). Resins are most often used as adjuncts to statins in patients who require additional lowering of LDL cholesterol. Since these drugs are not absorbed, adverse effects are limited to the gastrointestinal tract (Table 9-9). About 20%... 

The testes and adrenal glands produce 90% and 10%, respectively, of circulating testosterone. Testosterone enters prostate cells, where predominantly type II 5a-reductase activates testosterone to dihydrotestosterone, which combines with a cytoplasmic receptor. The complex enters the nucleus and induces changes in protein synthesis which promote glandular tissue growth of the prostate. Thus, 5a-reductase inhibitors (e.g., finasteride and dutas-teride) directly interfere with one of the major etiologic factors of BPH. 

Hormonal Does not occur in eunuchs. Low incidence in cirrhotic patients. Up to 80% are hormonally dependent. African-Americans have 15% increased testosterone. Japanese have decreased 5-a-reductase activities. Polymorphic expression of the androgen receptor. 

Fasco M. J., Hildebrandt E. F Suttie J. W. Evidence that warfarin anticoagulant action involves two distinct reductase activities. J Biol Chem 1982 257, 11210-2. 

Figure 1.5 Interactions of the dihydrofolate reductase active site with the inhibitor methotrexate (left) and the substrate dihydrofolate (right).

To provide a model for nitrite reductases72 Karlin and co-workers characterized a nitrite-bound complex (226) (r = 0.05)214 In an endeavor to model nitrite reductase activity, Tanaka and co-workers prepared a few mononuclear complexes (227) (r = 0.74)215 (228) (r = 0.82),216 (229) (r = 0.97),217 (230) (r = 0.16),217 (231) (r = 0.07),217 and (232) (r = 0.43 and r = 0.53)217 and studied the electrochemical reduction of N02A As a part of their activity on modeling heme-copper terminal oxidases, Holm and co-workers prepared complex (233) (r = 0.96).218 Using a sterically hindered tris(pyridylmethyl)amine, Canary et al. prepared a complex (234) (r=1.00), studied its redox behavior, and discussed various factors that may contribute to the difference (higher potential for the new complex) in the redox potential of a Cu Cu1 couple between substituted and unsubstituted ligands.2 9... 

The ent-fes-fep gene cluster is necessary for the synthesis of enterobactin and transport of the iron loaded siderophore. The fes gene product was shown to be necessary for utilization of the siderophore-bound iron inside the cell. The protein has an esterase activity which cleaves the ester bonds of the cyclic 2,3-dihydroxybenzoylserine ester in enterobactin. However, the esterase activity of Fes does not seem to be important for iron mobilization since Fes is also necessary for the utilization of iron from enterobactin analogues which do not have ester bonds (Heidinger et ah, 1983). No reductase activity has been found in Fes (Brickman and McIntosh, 1992) or in any other protein encoded in the ent-fes-fep gene cluster. 

There is some evidence that the iron-sulfur protein, FhuF, participates in the mobilization of iron from hydroxamate siderophores in E. coli (Muller et ah, 1998 Hantke, K. unpublished observations). However, a reductase activity of FhuF has not been demonstrated. Many siderophore-iron reductases have been shown to be active in vitro and some have been purified. The characterization of these reductases has revealed them to be flavin reductases which obtain the electrons for flavin reduction from NAD(P)H, and whose main functions are in areas other than reduction of ferric iron (e.g. flavin reductase Fre, sulfite reductase). To date, no specialized siderophore-iron reductases have been identified. It has been suggested that the reduced flavins from flavin oxidoreductases are the electron donors for ferric iron reduction (Fontecave et ah, 1994). Recently it has been shown, after a fruitless search for a reducing enzyme, that reduction of Co3+ in cobalamin is achieved by reduced flavin. Also in this case it was suggested that cobalamins and corrinoids are reduced in vivo by flavins which may be generated by the flavin... 

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