Purification and properties of galactose 1-phosphate uridyl transferase from Escherichia coli.

Gdactose l-phosphate uridyl transferase found in galactoseadapted yeast by Kalckar et al. (l), catalyzes the following reaction: UDP-glucose + galactose*-1-P ti UDP-galactose + glucose-1-P. A method for partial purification of galactose l-phosphate uridyl transferase from calf liver and application of this enzyme to the determination of galactose l-phosphate have been described (2). In the latter work it was indicated that this method can be applied for the determination of galactokinase activity in a two-step analysis involving an incubation for the formation of galactose l-phosphate from adenosine triphosphate and galactose followed by its determination (24). As the partially purified galactose l-phosphate uridyl transferase from calf liver is contaminated by galactokinase, a one-step assay of galactokinase activity was not possible. This paper deals with the partial purification of galactose lphosphate uridyl transferase from an Escherichia coli K12 galactokinase-less mutant and its application in the measurement of galactokinase activity. Some of the properties of the partially purified galactose l-phosphate uridyl transferase are also presented.