D-Glucose-6-phosphate dehydrogenase is a regulatory enzyme of the oxidative pentose phosphate pathway in Schizasaccharomyces pombe. The enzyme is subject to negative cooperative regulation by D-glucose-6-phosphate as characterized by the Hill coefficient of 0.68 +/- 0.04. D-Glyceraldehyde-3-phosphate and D-ribulose-5-phosphate rectify the negative cooperativity as evidenced from a change in the Hill coefficients to 0.98 +/- 0.05 and 1.02 +/- 0.05, respectively. These pentose phosphate pathway intermediates also inhibit the enzyme competitively with respect to D-glucose-6-phosphate. Thus, D-glucose-6-phosphate dehydrogenase provides an avenue for regulating the partitioning of D-glucose between the redundant branches of the oxidative phosphate pathway in S. pombe.