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 L_IV 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 (K_i, μM) and the inactivation rate constants (k_inact, 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.