Cellulose synthesis by extracts of Acanthamoeba castellani during encystment. Stimulation of the incorporation of radioactivity from UDP-[ 14C]glucose into alkali-soluble and insoluble β-glucans by glucose 6-phosphate and related compounds

Abstract

1. 1. The activity of a particulate enzyme prepared from encysting cells of Acanthamoeba castellanii (Neff), previously shown to catalyze the incorporation of glucose from UDP-[ 14C]glucose into both alkali-soluble and alkali-insoluble β-(1 → 4) glucans, was stimulated several fold by glucose-6-phosphate and several related compounds. 2. 2. Incorporation was observed when [ 14 C] glucose-6-P was incubated with the particles in the presence of UDP-glucose. The results of product analysis by partial acid hydrolysis indicated that glucose-6- P stimulates the formation of both alkali-soluble and alkali-insoluble β-(1 → 4) glucans from UDP-[ 14C]-glucose and was itself incorporated into an alkali-insoluble β-(1 → 4) glucan. 3. 3. When particles incubated with UDP-[ 14C]glucose and glucose-6- P were reisolated and then reincubated with unlabeled UDP-glucose and glucose-6- P, a loss of counts from the alkali-soluble fraction was detected along with a corresponding rise in the radioactivity of the alkali-insoluble fraction. This suggests that the alkali-soluble β-glucan was converted to an alkali-insoluble product and possibly may be an intermediate stage in cellulose synthesis.