title: Glucose-6-phosphate dehydrogenase from the chemolithotroph Thiobacillus ferrooxidans.
abstract: Glucose-6-phosphate dehydrogenase was partially purified from both glucose-grown and iron-glucose-grown Thiobacillus ferrooxidans. The enzyme possesses a dual nucleotide specificity for either nicotinamide adenine dinucleotide phosphate (NADP) or nicotinamide adenine dinucleotide (NAD) and has a molecular weight of 110,000 as determined by gel electrophoresis. Evidence is presented that T. ferrooxidans glucose-6-phosphate dehydrogenase is identical when isolated from cells grown mixotrophically (iron-glucose grown) or cells grown heterotrophically (glucose-grown cells). The enzyme is activated by Mg(2+), and to a lesser extent by low concentrations of Mn(2+). Reduced NAD inhibits the enzyme from T. ferrooxidans. No deviation from normal Michaelis-Menten kinetics was observed in velocity versus substrate concentration experiments. Adenosine triphosphate exerted a profound inhibition of the enzyme; the effect was 10 times more pronounced in the presence of NAD as compared to NADP. The physiological significance of this inhibition is discussed.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000249:Adenosine Monophosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000645:Ammonium Sulfate; D002130:Calcium Phosphates; D002474:Cell-Free System; D002850:Chromatography, Gel; D003470:Culture Media; D004589:Electrophoresis, Disc; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism / Q000494:pharmacology; D009249:NADP / Q000378:metabolism; D013053:Spectrophotometry; D013855:Thiobacillus / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D014461:Ultracentrifugation
chemical_list: D002130:Calcium Phosphates; D003470:Culture Media; D009243:NAD; D000249:Adenosine Monophosphate; D008345:Manganese; D009249:NADP; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D007501:Iron; D005954:Glucosephosphate Dehydrogenase; D008274:Magnesium; D005947:Glucose; D000645:Ammonium Sulfate