Glycosyl Phosphorylases

Several simple deoxyfluoro sugars and glycosyl fluorides were utilized " as probes for hydrogen bonding in the glycogen phosphorylase-o-glucose complex. 

Kinetics. In a double-displacement mechanism the enzyme shuttles between free enzyme and the intermediate carrying the substrate fragment (here, the glycosyl enzyme). With sucrose phosphorylase the maximum velocity varies with the concentrations of sucrose and HP042 in the characteristic fashion expected for this "ping-pong" mechanism (Eq. 9-47)43... 

The large variety of biological activities found in these compounds and many of their derivatives was discovered to be based on their potent glycosidase [58,157], glycosyl transferase [158] and phosphorylase [159] inhibitory activities. 

Enzyme-catalyzed glycoside cleavages (and syntheses) are considered by Hehre [6,8] to be variants of the same reaction (O Eq. 1), catalyzed by a single type of enzyme, the glycosylases, comprising glycoside hydrolases, glycosyl transferases, phosphorylases and certain lyases. 

Thus, X may be a saccharide, a 1,2-glycal, a phosphate residue, a nucleoside diphosphate, or a polyprenol diphosphate and X the OH of water, an alcohol, and often a saccharide. It is convenient, however, to consider enzymes cleaving polysaccharide chains in one of four classes hydrolases, glycosyl transferases, lyases, and phosphorylases. These follow the general reactions discussed below. 

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