Q-Enzyme, which converts amylose into amylopectin and which, with phosphorylase and glucose-1 phosphate, is responsible for the synthesis of amylopectin, has been isolated (as a stable freeze-dried powder) from the broad bean and the wrinkled pea. These preparations exert the same function as the Q-enzyme of potato. The phosphorylase of bean has also been isolated and shown to be closely similar to that of the potato. It is concluded that the mechanism of starch synthesis in these three plants is the same. Methods of removing α-amylase impurity from phosphorylase and Q-enzyme preparations have been investigated and a reliable test for α-amylase in the presence of other enzymes is described. The phosphorylase has been almost entirely freed from α-amylase, but a complete separation of this impurity from Q-enzyme has not been achieved. In the course of these investigations the presence of a "debranching" enzyme has been established. This will be the subject of a later communication.
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