Purification and Characterization of an α-Amylase Inhibitor (Haim) Produced by Streptomyces griseosporeus YM-25

Abstract

Haim, a microbial animal α-amylase inhibitor, was purified from the culture filtrate of Streptomyces griseosporeus YM-25 by salting out with ammonium sulfate, and column chromatographies on DEAE-cellulose, TEAE-cellulose and Sephadex G-50. Haim was separated into two fractions, Haim I and Haim II, by the TEAE-cellulose column. The preparations were homogeneous on disc electrophoresis and sedimentation by ultracentrifugation. The molecular weights of the inhibitors were estimated to be about 8, 500 by gel filtration and acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS), and about 8, 000 by sedimentation equilibrium studies. Isoelectric points of Haim I and Haim II were pH 4.0 and pH 3.8, respectively. Haim I and Haim II consisted of 75 and 77 amino acid residues, respectively, and contained no lysine or methionine residues. Neither Haim contained any carbohydrate moiety as an integral part of the protein molecule. Haim retained above 80% of its inhibitory activity after being treated at 100°C for 10 min in the pH range of from 2.5 to 7.9.