Inhibitors synthesized by the Streptomyces lucensis VKPM AS-1743 and Streptomyces violaceus VKPM AS-1734 strains were studied for their influence on amylases of different origin. The effect of the inhibitors was shown to be different on fungal amylase, pancreatic amylase, and amylase from human blood. It has been found that the studied inhibitors are substances of a pseudooligosaccharide nature and exhibit their activity and stability over a wide range of pH and temperature values. The physico-chemical and biochemical properties of isolated inhibitors were compared with those of known microbial inhibitors of α-glucosidases.