Characteristics of cellobiose phosphorylase.

The phosphorolysis of cellobiose was first demonstrated by Sih and McBee (1955a, b). These workers found that cellobiose phosphorylase was present in cell-free extracts of Clostridium thermocellum. Recently cellobiose phosphorylase has been reported from two other bacteria, Ruminococcus flavefaciens (Ayers, 1958, 1959), and Cellvibrio gilvus (Hulcher and King, 1958). This enzyme also catalyzes the synthesis of cellobiose froin a-D-glucose 1-phosphate and glucose (Sih, Nelson, and McBee, 1957; Ayers, 1959). In the present work, the stoichiometry of the reaction and the effect of physical and chemical agents on the activity of the enzyme were studied. Studies on the specificity of the enzyme revealed that D-glucose, D-xylose, L-xylose, 2-deoxyglucose, D-glucosamine, arsenate, and inorganic phosphate can act as substrates. Evidence has been obtained which indicates that the reaction proceeds by a single displacement mechanism. A preliminary report of this work has been published (Alexander, 1958).