Increase in β-N-Acetylglucosaminidase Activity during Germination of Cotton Seeds

A marked increase in beta-acetylglucosaminidase (2-acetamido-2-deoxy-beta-d-glucoside acetamidodeoxyglucohydrolase, EC 3.2.1.30) activity was observed in the germinating cotyledon of cotton seeds. The enzyme was isolated from cotton seedlings and purified to study its physiological function in the germination of cotton seeds. The purification procedure involves ammonium sulfate fractionation, ion-exchange chromatography, gel filtrations, and concanavalin A-Sepharose 4B chromatography, and the purified beta-N-acetylglucosaminidase was shown to be homogeneous by disc electrophoresis. The molecular weight was estimated to be about 125,000 by gel filtration. The enzyme hydrolyzed both p-nitrophenyl-N-acetyl-beta-d-glucosamine and p-nitrophenyl-N-acetyl-beta-d-galactosamine. When p-nitrophenyl-N-acetyl-beta-d-glucosamine was used as substrate, K(m) and V(max) were 0.625 nanomolar and 228 moles per minute per milligram, respectively, and optimum activity was at pH 5.6. The enzyme liberated beta-linked N-acetyl-glucosamine from chitin, ovalbumin, and pronase-digested wheat germ lectin.