title: Characterization of a thermolabile sulfite reductase from Salmonella pullorum.
abstract: The biochemical basis for sulfite accumulation by sulfate-using revertants of Salmonella pullorum was determined. All of the sulfate-using mutants isolated from wild-type S. pullorum accumulated sulfite when grown at 37 but not at 25 C. The specific activity of reduced nicotinamide adenine dinucleotide (NADPH)-dependent sulfite reductase (H (2)S-NADP oxidoreductase, EC 1.8.1.2) and of reduced methyl viologen (MVH)-dependent sulfite reductase (H (2)S-MV oxidoreductase), in extracts prepared from cells incubated at 37 C, declined as the incubation period lengthened. However, the specific activity of both reductases from cells incubated at 25 C did not decline. Thermolability of cell-free NADPH-dependent sulfite reductase from cells of S. pullorum incubated at 37 C was greater than the lability of this enzyme either from cells of S. typhimurium incubated at 37 C or from cells of S. pullorum incubated at 25 C. Cells cultured at 37 C continued to accumulate sulfite when the incubation temperature was shifted to 25 C; cells cultured at 25 C and shifted to 37 C accumulated no sulfite, whereas these cells shifted to 41 C accumulated sulfite. It was concluded that the configuration of the sulfite reductase of S. pullorum strain 6-18 is a function of the incubation temperature at which synthesis occurs.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D002474:Cell-Free System; D002701:Chloramphenicol / Q000494:pharmacology; D003470:Culture Media; D005827:Genetics, Microbial; D007202:Indicators and Reagents; D009154:Mutation; D010088:Oxidoreductases / Q000378:metabolism*; D012475:Salmonella / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D012694:Serine; D013431:Sulfates / Q000378:metabolism; D013447:Sulfites / Q000096:biosynthesis; D013696:Temperature; D013997:Time Factors
chemical_list: D003470:Culture Media; D007202:Indicators and Reagents; D013431:Sulfates; D013447:Sulfites; D012694:Serine; D002701:Chloramphenicol; D010088:Oxidoreductases; D000217:Acyltransferases