The b.e. and Q types of 1,4-α-d-glucan: 1,4-α-d-glucan-6-glucosyltransferase isozymes in algae

The branching isozymes of the red alga, Rhodymenia pertusa are of two types: Q, which can branch, via the synthesis of α-1,6-glucosyl linkages, linear amyloses to amylopectin; and b.e., which can further branch the amylopectin formed to the more highly-branched floridean starch. Using the technique of tandem crossed-immunoelectrophoresis, it is shown that the Q branching isozyme of the red alga is more closely related to the b.e. type of branching isozymes of Anacystis nidulans and Cyanidium caldarium than it is to the exclusively Q types of branching isozymes found in Chlorella pyrenoidosa and other chlorophytes. The possibility of a biphyletic evolution of the red and the green algae from blue-green ancestral forms is discussed.