Isolation and properties of a new .BETA.-galactosidase inhibitor, galactostatin, from Streptomyces lydicus.

Abstract

A new β-galactosidase inhibitor was found with a newly developed rapid and practical screening method for β-galactosidase inhibitors. Several strains of Actinomycetes that produced βgalactosidase inhibitors were isolated from soil samples using this method, and Streptomyces lydicus PA-5726 was found to produce a high concentration of new inhibitor in the culture medium. Improvement of the medium led to 20-25-fold augmentation (45 to 900-1, 100μg/ml) of the production. This new inhibitor, which was named galactostatin, was isolated by adsorption on Dowex-50W×8 (H+), crystallization from the bisulfite adduct, development on Dowe×-2 × 8 (OH-) and precipitation with EtOH. Galactostatin displayed strong inhibitory activity toward several β-galactosidases in acidic and neutral media but low acute toxicity in mice (LD50 1016mg/kg, i.v.).