Properties of glucosyltransferase and glucan transferase from spinach.

A glucosyl and a glucosyl-glucan transferase activity from spinach (Spinacia oleracea L. var. Matador) leaves have been partially purified and characterized. The latter activity (fraction 1 after diethylaminoethylcellulose chromatography) is responsible for the transfer of glucosyl as well as of maltosyl, maltotriosyl, and higher homologous residues to glucose giving rise to maltose and the correspondingly larger molecules. This fraction also shows beta-amylase activity. The transfer takes place only to glucose; maltose, as well as other alpha-1,4-glucans, serve as donors. The enzyme fraction 2 is amylase-free and catalyzes only the transfer of glucosyl moieties, again with high acceptor specificity to glucose. Maltose and larger alpha-1, 4-glucans, with the exception of maltotriose and maltotetraose, act as donors. The physiological function of these enzymes may be the formation of oligosaccharide primers for starch synthetase or phosphorylase.