Cyclic diguanylic acid stimulates 1,4-β-glucan synthase from Saprolegnia monoica Free

1,4-β-Glucan synthase activity, but not 1,3-β-glucan-synthase activity, from Saprolegnia monoica was stimulated by cyclic-diguanylic acid, an immediate activator of Acetobacter xylinum- cellulose synthase. This activator, which increased the V_max without modifying the K_m for UDP-glucose, was active on solubilized and partially purified enzymes. These results suggest that the fungal system shares a common regulatory mechanism with the bacterial system.