Abstract
Hexose 1-phosphate uridylyltransferase (EC 2.7.7.12) was present constitutively in Bifidobacterium bifzdum. The enzyme was purified to a homogeneous state from B. bifzdum grown on a glucose medium and characterized. The molecular weight of the enzyme is about 110, 000. The pH optimum of the enzyme was 7.5. The enzyme was very labile on the acidic side below pH 4.5. Thymidine diphosphate glucose could serve as a substrate with about 60 efficiency of UDP-glucose. The Km values for UDP-glucose, galactose 1-phosphate (Gal-1-P), UDP-galactose and glucose 1-phosphate (Glc-1-P) were estimated to be 2.3×10-5M, 5.0×10-4M, 3.1×10-5M and 1.4×10-4M, respectively. From these results the physiological roles of the enzyme were considered in relation to galactose metabolism in B. bifidum.
