Multiple forms of α-1,4 glucan synthetase from spinach leaves

ADP-glucose:α-1,4 glucan-4-glucosyl transferase was extracted from spinach leaves and separated by gradient elution on a DEAE-cellulose column. Fractions I and II gave equal activity with amylose, amylopectin, or glycogen as a primer while the activity of fraction III with glycogen as primer was only 25% of the activity observed with amylose or amylopectin as primer. Glucan synthesis in the absence of primer was found in fraction III. This activity was stimulated over 1000-fold by bovine plasma albumin and high salt concentrations. The radioactive unprimed product was a glucan with principally α-1,4 linkages and some α-1,6 linkages.