STIMULATION OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE BY OXYHEMOGLOBIN

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key glycolytic e nzyme regulated by many diverse mechanisms. In this study we present e vidence that GAPDH activity is stimulated in the presence of oxyhemogl obin (2.3-fold, P<0.005). No stimulation was seen by myoglobin, and on ly slight stimulation (1.2-fold, not significant) by methemoglobin was observed. Such stimulation may have physiological significance as 1,3 -bis-phosphoglycerate, the product of GAPDH, isomerises to 2,3-bis-pho sphoglycerate, an allosteric effector that decreases the oxygen affini ty of hemoglobin, thus providing a feedback loop. The results suggest that when assaying GAPDH activity in biological samples, hemoglobin co ntent should be taken into account. (C) 1997 Federation of European Bi ochemical Societies.