Glactose And Fructose Metabolism

Once it is transported into tissues it’s phosphorylated by galactokinase into galactose 1 p and then converted to glucose 1 p by galactose 1 p URIDYLTRANSFERASE AND EPIMERASE and then it can used in glycogen synthesis or converted to glucose 6 p to enter glycolysis Deficiency of these enzymes lead to galactosemia ( the body can’t deal with galactose thus there is elevated amounts in blood , urine and there is hypoglycemia due to decreased glucose synthesis

Cataracts is a characteristic symptom with galactosemia, results from converting excess galactose to galactitol by aldose reductase in lens and thus accumulation of it causing osmotic damage and cataract

Diabetic patients suffer from cataract as glucose is converted to sorbitol by Aldose reductase in lens and then accumulation of it causing osmotic damage and cataract

Once transported to tissues, it is phosphorylated by either hexokinase or fructokinase ( known as keto hexokinase) Hexokinase converts it to fructose 6 p and then PFK-1 phosphorylated to fructose 1,6 bip and so on Fructokinase converts it to fructose 1 p and then it is cleaved by aldolase B in liver and kidney to DAHP and glyceraldehyde only , later glyceraldehyde can be phosphorylated and so on The rate of fructose metabolism by fructokinase is more rapid than glucose metabolism as fructose 1 p bypass PFK-1 the rate limiting enzyme

In liver , kidney and small intestine