The Effect of Pentacyclic Guanidine Alkaloids from the Marine Sponge Monanchora pulchra Lambe, 1894 on the Activity of Natural β-1,3-D-glucanase from the Marine Fungus Chaetomium indicum Corda, 1840 and the Marine Bivalve Mollusk Spisula sachalinensis, Schrenck, 1861

Abstract

The effect of pentacyclic guanidine alkaloids monanchomycalin B, monanchocidin A and normonanchocidin A isolated from the Far-Eastern marine sponge Monanchora pulchra was investigated towards the activity of exo-β-1,3-D-glucanase from the filamentous marine fungus Chaetomium indicum and endo-β-1,3-D-glucanase LIV from the marine bivalve mollusk Spisula sachalinensis. All compounds were shown to be slow irreversible inhibitors of exo-β-1,3-D-glucanase and significantly activated endo-β-1,3-Dglucanase. The equilibrium inhibition constants (Ki, μM) and the inactivation rate constants (kinact, min–1) were determined for each compound. The inhibitory capacities of alkaloids were shown to depend on the structure of the “anchor” part of the molecule of the compounds. Normonanchocidin A was the best inhibitor of exo-β-1,3-D-glucanase from fungi. A possible biological role of these compounds in the life of sponges and their microbial symbionts is discussed here.