Kinetic studies of gluconate pathway enzymes from Schizosaccharomyces pombe.
Glucose dehydrogenase and gluconate kinase which catalyze two-step reactions of the gluconate pathway have been purified from Schizosaccharomyces pombe. Their steady-state kinetic studies were undertaken. The yeast glucose dehydrogenase requires NADP+ as an obligatory coenzyme and mediates the oxidation of D-glucose to D-gluconate via an ordered Bi Bi mechanism with NADP+ as the leading substrate. Kinetic constants for the dehydrogenase reactions have been measured. The yeast gluconate kinase requires Mg2+ as an activator. The phosphorylation catalyzed by the fission yeast gluconate kinase has been studied kinetically at a fixed concentration of Mg2+. The initial velocity and product inhibition results are consistent with a rapid equilibrium random Bi Bi mechanism with the formation of an abortive enzyme-ADP-gluconate complex. Dissociation constants of the two substrates, ATP and D-gluconate from various binary and ternary enzymic complexes, have been determined.
Tsai
C S
CS
Department of Chemistry, Carleton University, Ottawa, Ontario, Canada.
Shi
J L
JL
Ye
H G
HG
D000244:Adenosine Diphosphate / Q000378:metabolism; D005942:Gluconates / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D042843:Glucose 1-Dehydrogenase; D005948:Glucose Dehydrogenases / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000302:isolation & purification / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000201:enzymology*; D013379:Substrate Specificity
D005942:Gluconates; D009249:NADP; D000244:Adenosine Diphosphate; D005948:Glucose Dehydrogenases; D042843:Glucose 1-Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C020578:gluconokinase; D008274:Magnesium; D005947:Glucose; C030691:gluconic acid