Mannostatins A and B: New inhibitors of .ALPHA.-D-mannosidase, produced by Stereptoverticillium verticillus var. quintum ME3-AG3: Taxonomy, production, isolation, physico-chemical properties and biological activities.

Mannostatins have been isolated as part of a program designed to find microorganism-produced inhibitors of alpha-D-mannosidase from Streptoverticillium verticillus var. quintum. They were purified by sequential use of active carbon and Dowex resins and then isolated as colorless powders. Mannostatins A and B have the molecular formula, C6H13NO3S and C6H13NO4S, respectively. They were competitive with the substrate, and the inhibition constants (Ki) of mannostatins A and B were 4.8 x 10(-8) M.