Galactose Metabolism

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The major source of galactose is lactose (a disaccharide of glucose and galactose) obtained from milk and milk products, enters glycolysis by its conversion to glucose-1-phosphate (G1P).

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Galactose Metabolism By: Gulzar Alam

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The major source of galactose is lactose (a disaccharide of glucose and galactose) obtained from milk and milk products, enters glycolysis by its conversion to glucose-1-phosphate (G1P). This occurs through a series of steps. First the galactose is phosphorylated by galactokinase to yield galactose-1-phosphate. Epimerization of galactose-1-phosphate to G1P requires the transfer of UDP from uridine diphosphoglucose (UDP-glucose) catalyzed by galactose-1-phosphate uridyl transferase . This generates UDP-galactose and G1P. The UDP-galactose is epimerized to UDP-glucose by UDP- galactose-4 epimerase . The UDP portion is exchanged for phosphate generating glucose- 1-phosphate which then is converted to G6P by phosphoglucose mutase . Galactose Metabolism

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Galactose-1-phosphate uridyl transferase Pathway of Galactose Metabolism

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Galactosemia Galactosemia (means "galactose in the blood “) is an inherited disorder characterized by an inability of the body to utilize galactose. Galactosemia is a condition seen in around 1 of 40-50000 of newly born children.  These children possess intestinal  lactase activity and can split lactose and take up the liberated galactose and glucose. Galactosemia arise due to lack of either hepatic galactosyl uridylyltransferase (classical galactosemia ) or galactokinase (non-classical galactosemia ). Thus, Impaired hepatic galactose metabolism ( galactosemia ) leads to high circulating levels of galactose. Clinical findings of these disorders include impaired liver function, elevated blood galactose, hypergalactosemia, urinary galactitol excretion and hyperaminoaciduria . Aldose reductase , found in the eye, converts galactose to galactitol . Galactitol accumulate in the lens, leading to increased osmotic pressure, protein denaturation and cataract formation.