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.
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