Disaccharide phosphorylases

It seems quite possible that not only true phosphorylase but also other transglycosidases may play an important role in the biological syntheses, decompositions and interconversions of disaccharides and polysaccharides. 

R. flavefaciens cells, during growth in pure culture, released cellulase, endoglucanase, and xylanase into the culture fluid. This microorganism hydrolyzed cellulose to yield only cellobiose as a product 49). It had been reported that a ceUobiose phosphorylase and glucokinase were present in R flavefaciens (8). The Ruminococcus cellulase system was repressed by disaccharides such as cellobiose, sucrose, and lactose 50). 

When a mixture of UDPG and D-fructose is subjected to the reaction of enz3nne preparations from these plant sources in the presence of inorganic phosphate buffer at pH 7.0, a nonreducing disaccharide, identified as sucrose, is formed. The equilibrium constant, Ky for this reaction at 37°C was found to be between 2 and 8, and the AF was estimated to be approximately —1000 cal. as compared to +1770 cal. for the sucrose phosphorylase reaction. In contrast to the sucrose phosphorylase reaction, the equilibrium of the reaction starting with UDPG and D-fructose is in favor of sucrose synthesis. 

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