Kinetics of human erythrocyte glucose-6-phosphate dehydrogenase dimers.
The steady-state kinetics of human erythrocyte glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49) dimers were studied by initial rate measurement. These experiments gave intersecting double-reciprocal plots suggesting a ternary complex mechanism with a Km for NADP and glucose 6-phosphate of 11 microM and 43 microM, respectively. These studies were combined with rate measurements in the presence of one product (NADPH), dead-end inhibitors, as well as alternative substrates. The inhibition by NADPH was found to be competitive with respect to both substrates. Alternate substrates experiments gave linear double-reciprocal plots over a wide range of substrate concentrations. The results suggest that the dimeric enzyme follows either a random or a Theorell-Chance mechanism.
Birke
S
S
Department of Chemistry Occidental College, Los Angeles, CA 90041.
Kim
H W
HW
Periclou
A
A
Schorsch
B
B
Grouse
D
D
Craney
C
C
D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000201:enzymology*; D019298:Glucose-6-Phosphate; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000097:blood; D005958:Glucosephosphates / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009249:NADP / Q000494:pharmacology; D011485:Protein Binding
D005958:Glucosephosphates; D009249:NADP; D019298:Glucose-6-Phosphate; D005954:Glucosephosphate Dehydrogenase