The role of D-enzyme in starch metabolism in plants

D-enzyme (EC 2.4.1.25) is believed to be involved in starch metabolism, but the function in vivo is not known. In order to investigate the role of D-enzyme, several approaches have been undertaken. A biochemical analysis of the purified potato D-enzyme suggested that high molecular weight starch (amylose and amylopectin) can serve as donor and acceptor, and very long α-1, 4-glucans or even highly branched glucans can be transferred by the enzyme. Transgenic potato plants with dramatically reduced D-enzyme activity were obtained by introducing sense and antisense D-enzyme cDNA sequences with the appropriate promoter sequence. The tubers from these plants sprouted later and the growth of sprouts was slower than the wild type. However, no significant difference was found in starch produced in tubers, either in its quantity or quality. From these results, the possible role of Denzyme in starch metabolism is discussed.