Galactose enzymic phosphorylation

Once transported into tissues, galactose is phosphorylated (galactokinase), trapping it in the cell. Galactose 1-phosphate is converted to glucose 1-phosphate by galactose 1-P uridyltrans-ferase and an epimerase. The pathway is shown in Figure 1-12-5 important enzymes to remember are ... 

Cardini, C. E. and Leloir, L. F. 1952. Enzymic phosphorylation of galactosamine and galactose. Arch. Biochem. Biopkys. 45, 55-64. 

A type of reaction which is applicable in many cases is the phosphorylation with ATP using different kinases. In this manner many esters can be obtained from the free sugars such as glucose 6-phosphate, mannose 6-phosphate, fructose i-phosphate, fructose 6-phosphate, fructose i,6-diphosphate, galactose i-phosphate, galactosamine i-phosphate, gluconic acid 6-phos-phate, ribose 5-phosphate and ribulose 5-phosphate. A special case of enzymic phosphorylation in which a pyrophosphate residue is transferred from ATP is the following reaction ... 

D-Galactose, a product of hydrolysis of the disaccharide lactose (milk sugar), passes in the blood from the intestine to the liver, where it is first phosphorylated at C-l, at the expense of ATP, by the enzyme galactokinase ... 

Like fructose, galactose must be phosphorylated before it can be fur ther metabolized. Most tissues have a specific enzyme for this pur pose, galactokinase, which produces galactose 1-phosphate (Figure 12.5). ATP is the phosphate donor. 

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