PURIFICATION AND CHARACTERIZATION OF 2 FORMS OF MALTOTETRAOSE-FORMING AMYLASE FROM PSEUDOMONAS-STUTZERI

Pseudomonas stutzeri MO-19 produced two active forms of extracellular maltotetraose-forming amylase. Both forms, G4-1 and G4-2, were purified to electrophoretic homogeneity. The molecular masses of G4-1 and G4-2 were 57kd and 46kd by SDS-polyacrylamide gel electrophoresis, respectively. An identical N-terminal sequence up to 20 amino acid residues and similar amino acid compositions were obtained from both forms, but different C-terminal amino acids, leucine from G4-1 and alanine from G4-2, were released by carboxypeptidase Y. By in vitro incubation with a culture supernatant containing protease activity, G4-1 was converted into G4-2 without any loss of the amylase activity. It was concluded that G4-2 was a product derived by the limited proteolysis of G4-1, and that the proteolysis occured in the C-terminal region of G4-1. G4-2 was more thermostable than G4-1, and had a 20-fold higher Michaelis constant value for glycogen, which was 50 mg/ml against 2.3 mg/ml of G4-1. G4-1 adsorbed onto raw starch granules while G4-2 did not. © 1990 by the Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.