The hexosediphosphate metabolism of normal tissue extracts

Abstract

Dialyzed normal tissue extracts prepared at 20[degree] do not convert glucose to lactic acid either at 38 or 50-55[degree] in presence or absence of glutathione. With the exception of blood, which has no glycolytic activity under these conditions, all dialysed tissue extracts formed small amts. of lactic acid from hexosediphosphate at 50-55[degree], and addition of glutathione causes a large increase in activity. Little lactic acid is formed from hexosediphosphate at 38[degree] and the yield is not increased by addition of glutathione. The coenzyme effect of glutathione commences at 0.027 mg GSH per ml. Below this conc. glycolysis is dependent upon a thermo-labile system not influenced by glutathione. Formation of alkali-labile phosphoric esters from hexosediphosphate is very rapid at 52[degree] in liver extract containing citrate or bicarbonate. Addition of glutathione causes no change in alkali-labile phosphoric ester conc. The same amt. of inorganic phosphate is formed from hexosediphosphate by liver extract at 52[degree] in presence or absence of glutathione. Almost the whole of the enzymic activity remains in the uncoagulated portion of tissue extracts heated for 30 min. at 51[degree]. Cysteine cannot replace glutathione as coenzyme for conversion of hexosediphosphate to lactic acid at 50-55[degree]. No methylglyoxal is formed by liver extract from hexosediphosphate at 50.5[degree] in absence of glutathione. The activity of tissue extracts which convert hexosediphosphate into lactic acid at 50-55[degree] in presence of glutathione increases greatly on dilution of the enzyme.