The Enzyme Catalyzing Uridine Diphosphate Glucose and Uridine Diphosphate Galactose Pyrophosphorolysis in Bifidobacterium bifidum : Biochemical strdies on Bifidobacterium bifidum(II)

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Uridine diphosphate glucose (UDP-glucose) and uridine diphosphate galactose (UDP-galactose) pyrophosphorylase preparations were purified about 500-fold and 180-fold, respectively, from the cell-free extract of B. bifidum. The activity ratio of UDP-galactose pyrophosphorylase to UDP-glucose pyrophosphorylase was constant (about 1 : 3) throughout purification procedures. There was no significant difference in their properties such as pH optimum, cation requirement, effect of sulfhydryl reagents and stabilities under various conditions. The ratio of the two activities was varied with the substrate (UDP-galactose or UDP-glucose) concentration; the ratio was about 1 : 3 at 3.6 mM, about 1 : 1 at 8 mM, and at more than 8 mM, activity for UDP-galactose bacame higher than that for UDP-glucose. The Michaelis constants for UDP-glucose and UDP-galactose were about 1.11 mM and 12.5 mM, respectively. The V _<max> of UDP-galactose pyrophosphorylase activity was about twice that of UDP-glucose pyrophosphorylase activity. These findings are discussed in relation to the physiological significance of the enzyme in B. bifidum.
公益社団法人日本生物工学会の論文
1977-04-25