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1.
Rhodopseudomonas sulfoviridis is unable to grow with sulfate as sole sulfur source. Radioactively labelled sulfate is not incorporated into the cells. Growth only occurs in the presence of reduced sulfur compounds, such as sulfide, thiosulfate, elemental sulfur and cysteine. ATP sulfurylase, adenylylsulfate kinase, O-acetylserine sulfhydrylase and cysteine desulfhydrase are present. Adenylylsulfate sulfotransferase and thiosulfonate reductase are lacking. The enzymes of the sulfate-activating system are not derepressed by O-acetylserine.Non common Abbreviations APS Adenosine 5-phosphosulfate - PAPS 3-phosphoadenosine 5-phosphosulfate  相似文献   

2.
Summary The metabolic pathway of phenylmalonic acid byAlcaligenes bronchisepticus KU1201, which catalyzes the asymmetric decarboxylation of -aryl--methylmalonic acids to -arylpropionic acids, is demonstrated. Enantioselective oxidation of mandelic acid was investigated using the metabolizing pathway in this strain. Incubation of (±)-mandelic acid withA. bronchisepticus afforded optically pure (R)-one accompanied by benzoylformic acid and benzoic acid. This enzymatic oxidation is also applicable to various substituted mandelic acids.  相似文献   

3.
Thiobacillus tepidarius (type strain) was grown in microaerophilic conditions, on tetrathionate, thiosulfate or crystalline So. The rates of tetrathionate, thiosulfate, elemental sulfur (So) and sulfite oxidation of the different cultures were measured respirometrically, using exponentially growing cells, with an oxygen electrode. Cells growing on the three different sulfur compounds retain thiosulfate-, tetrathionate, and So-oxidizing activities (SOA), but lack respiratory sulfite-oxidizing activity. The SOA for all the cultures was almost totally inhibited by 50 M myxothiazol, an inhibitor of the quinone-cytochrome b region, and by 10 M of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Tetrathionate- and thiosulfate-oxidizing activities were moderately and weakly inhibited by 50 M totally inhibited (>95%) all respiratory activities. This study suggests that electrons released by So oxidation enter the respiratory chain in the quinone-cytochrome b region.Abbreviation SOA sulfur-oxidizing activity  相似文献   

4.
Summary The oxidized form of the mercuric ion binding protein MerP has been studied by two-dimensional NMR. MerP, which is a periplasmic water-soluble protein with 72 amino acids, is involved in the detoxification of mercuric ions in bacteria with resistance against mercury. The mercuric ions in the periplasmic space are first scavenged by the MerP protein, then transported into the cytoplasm by the membrane-bound transport protein MerT, and finally reduced to elementary (nontoxic) mercury by the enzyme mercuric reductase. In this work, the 1H NMR spectrum of oxidized MerP (closed disulfide bridge) has been assigned by using homonuclear 2D NMR techniques. The secondary structure and global fold have been inferred from the nuclear Overhauser effect (NOE) data. The secondary structure comprises four -strands and two -helices, in the order 112324. The protein folds into an antiparallel -sheet, 2314, with the two antiparallel helices on one side of the sheet. The folding topology is similar to that of acylphosphatase, the activation domain of porcine pancreatic procarboxypeptidase B, the DNA-binding domain of bovine papillomavirus-1 E2 and the RNA-binding domains of the U1 snRNP A and hnRNP C proteins. However, there is no structural similarity between MerP and other bacterial periplasmic binding proteins.  相似文献   

5.
Disproportionation of thiosulfate or sulfite to sulfate plus sulfide was found in several sulfate-reducing bacteria. Out of nineteen strains tested, eight disproportionated thiosulfate, and four sulfite. Growth with thiosulfate or sulfite as the sole energy source was obtained with three strains (Desulfovibrio sulfodismutans and the strains Bra02 and NTA3); additionally, D. desulfuricans strain CSN grew with sulfite but not with thiosulfate, although thiosulfate was disproportionated. Two sulfur-reducing bacteria, four phototrophic sulfur-oxidizing bacteria (incubated in the dark), and Thiobacillus denitrificans did not disproportionate thiosulfate or sulfite. Desulfovibrio sulfodismutans and D. desulfuricans CSN formed sulfate from thiosulfate or sulfite even when simultaneously oxidizing hydrogen or ethanol, or in the presence of 50 mM sulfate. The capacities of sulfate reduction and of thiosulfate and sulfite disproportionation were constitutively present. Enzyme activities required for sulfate reduction (ATP sulfurylase, pyrophosphatase, APS reductase, sulfite reductase, thiosulfate reductase, as well as adenylate kinase and hydrogenase) were detected in sufficient activities to account for the growth rates observed. ADP sulfurylase and sulfite oxidoreductase activities were not detected. Disproportionation was sensitive to the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) but not to the ATPase inhibitor dicyclohexylcarbodiimide (DCCD). It is proposed that during thiosulfate and sulfite disproportionation sulfate is formed via APS reductase and ATP sulfurylase, but not by sulfite oxidoreductase. Reversed electron transport must be assumed to explain the reduction of thiosulfate and sulfite by the electrons derived from APS reductase.Abbreviations CCCP Carbonylcyanide m-chlorophenylhydrazone - DCCD N,N-dicyclohexylcarbodiimide - APS adenosine 5-phosphosulfate (adenylylsulfate)  相似文献   

6.
Summary Intact cells of Thiobacillus denitrificans catalyzed the oxidation of thiosulfate, sulfide and sulfite with nitrate or oxygen as the terminal acceptor. The anaerobic oxidation of thiosulfate, sulfide and sulfite was sensitive to the inhibitors of the flavoprotein system. Under aerobic conditions the oxidation of sulfide and sulfite was sensitive to these inhibitors but the thiosulfate oxidation was unaffected. Cyanide and azide inhibited the aerobic and anaerobic respiration when thiosulfate, sulfide or sulfite served as electron donors. The oxidation of thiosulfate by cell-free preparations was mediated by cytochromes of c, a and o-types. The cell-free extracts also catalyzed the oxidation of NADH and succinate, involving flavoproteins and b, c, a and o-type cytochromes. In addition, a cytochrome oxidase sensitive to cyanide and azide was also present.Non-Standard Abbreviations TTFA Thenoyltrifluoroacetone - HQNO 2-heptyl-4-hydroxyquonoline N-oxide Aspirant van het Nationaal Fonds voor Wetenschappelijk Onderzoek (Belgian National Science Foundation).  相似文献   

7.
Incubation of highly purified -amylase fromAspergillus oryzae (EC 3.2.1.1) with 0.01M acetate buffer, pH 3.0, resulted in degradation of the -amylase. The molecular weight values of degradation products were 42 K, 37 K, and 28 K. Incubation of the purified -amylase in 0.02m phosphate buffer, pH 7.5, at 30°C for 17 h, however, resulted in no degradation of the -amylase molecule.Incubation of the purified -amylase with proangiotensin at pH 3.0 for 24 h resulted in cleavage of Tyr4-Ile5, His6-Pro7, Pro7-Phe8, Phe8-His9, and His9-Leu10. Thus, it appears that proteolytic activities firmly bound to -amylase are identical withAspergillus aspartic proteinase (EC 3.4.23.6) andAspergillus acid carboxypeptidase (EC 3.4.16.1).  相似文献   

8.
Summary A review is given of primary and associated electron transport reactions in various division of photosynthetic bacteria and in the two photosystems of plant photosynthesis. Two types of electron acceptor chains are distinguished: type Q, found in purple bacteria, Chloroflexus and system II of oxygenic photosynthesis and type F, found in green sulfur bacteria, Heliobacterium and photosystem I. Secondary donor reactions are discussed in relation to plant photosystem II.Dedicated to the memory of Warren L. Butler  相似文献   

9.
Summary Aerobic spore-forming bacteria were found dominant in the microflora of food packaging paper and board. Twenty-five strains of bacteria belonging to the genusBacillus were isolated from these paper and board machines, papermaking chemicals, and final products of papermaking. Nineteen strains were analyzed for production of -amylase, -glucosidase, glucoamylase, pullulanase, -glucanase, carboxymethyl cellulase, and caseinase, and also for resistance towards industrial biocides. pH and temperature optima for the activity of the enzymes were determined. All strains were found to produce one or more of the enzymes studied. The amylolytic enzymes of most strains had high temperature optima for activity. Vegetative cells of all strains were found very resistant towards the different commercial slimicides used in paper and board mills. This property together with the ability to survive through the dry end of the machine to the final board and paper, and the production of enzymes degrading papermaking chemicals makes these bacteria potentially harmful in paper and board mills.  相似文献   

10.
Transglutaminases   总被引:32,自引:0,他引:32  
Summary This paper is intended as a background to the topic of transglutaminases, while focusing on current ideas regarding the biological roles of these enzymes. Specifically, the following topics are discussed: geometry of forming -glutamyl--lysine cross-linked structures; energetic considerations; the -glutamyl--lysine cross-link; amine incorporation assays; artefactual incorporation of amines in cells and tissue homogenates; synthetic substrate systems; regulation of transglutaminase activities; strategies for probing transglutaminase-mediated events in biological systems; the blood clotting paradigm; transglutaminase and cell aging: the Ca2+-enriched human erythrocyte; transglutaminase and cell activation: the thrombin-stimulated human platelet and the fertilized sea urchin egg.  相似文献   

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