The effect of copper on human and bovine lens and on human cultured lens epithelium enzymes

The effect of physiological levels of copper on the glycolytic and shunt pathway enzymes of glucose metabolism in human and bovine lens and on cultured lens epithelium has been studied. In human and bovine lens homogenates, hexokinase, phosphofructokinase, pyruvate kinase, glyceraldehydephosphate dehydrogenase, phosphoglycerate kinase and 6-phosphogluconate dehydrogenase were almost completely inhibited in the presence of 50 μm-copper. Aldolase, glucose-6-phosphate dehydrogenase and triose phosphate isomerase were inhibited 78, 50 and 36% respectively. The inhibition of most of the enzymes was not significantly reversed by the addition of EDTA. The inhibition of enzyme activity was also not reversed by dialysis of the copper-treated enzyme against phosphate buffer. Similar results were obtained when human cultured lens epithelium was used as the enzyme source. The studies indicate that if the increased amount of copper present in senile cataractous lenses is in the free form, it can significantly impair glucose metabolism in the lens.