Purification and Characterization of Two Forms of Maltotetraose-forming Amylase from Pseudomonas stutzeri(Biological Chemistry)

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Pseudomonas stutzeri MO-19 produced two active forms of extracellular maltotetraose-forming amylase. Both forms, G_4-1 and G_4-2, were purified to electrophoretic homogeneity. The molecular masses of G_4-1 and G_4-2 were 57 kd and 46 kd 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 G_4-1 and alanine from G_4-2, were released by carboxypeptidase Y. By in vitro incubation with a culture supernatant containing protease activity, G_4-1 was converted into G_4-2 without any loss of the amylase activity. It was concluded that G_4-2 was a product derived by the limited proteolysis of G_4-1, and that the proteolysis occured in the C-terminal region of G_4-1. G_4-2 was more thermostable than G_4-1, and had a 20-fold higher Michaelis constant value for glycogen, which was 50mg/ml against 2.3mg/ml of G_4-1. G_4-1 adsorbed onto raw starch granules while G_4-2 did not.
社団法人日本農芸化学会の論文
1990-03-23