Novel .alpha.-1,6-glucosidase and process for producing the same

Abstract

A novel .alpha.-1,6-glucosidase having the following properties: (1) Action: The enzyme acts on an .alpha.-1,6-glucoside bond to produce linear amylose; (2) Substrate specificity: The enzyme has the following relative activity to polysaccharides: ______________________________________ Polysaccharide Relative activity (%) ______________________________________ Pullulan 100 Maize soluble amylopectin 13.5 Soluble starch 6.7 Oyster glycogen 1.7 Hare glycogen 2.6 Maize amylopectin 3.8 Potato amylopectin 4.0 ______________________________________ (3) Km value and Vmax to pullulan: the enzyme has Km value of 0.14 mg/ml and Vmax of 70.0 .mu.mol/min/mg protein; (4) Optimum pH: 5.0 to 5.5; (5) pH stability: The enzyme is stable in the pH range of 4.5 to 6.5 for 30 minutes at 40.degree. C. and in the pH range of 5.0 to 6.0 for 30 minutes at 50.degree. C.; (6) Optimum temperature: Approximately 55.degree. C.; (7) Thermal stability: Treatment at pH 4.5 for 30 minutes at different temperatures indicates that the enzyme retained 80% of the initial activity at 40.degree. C. and 10% thereof at 60.degree. C.; (8) Influence of inhibitor: The enzyme is inhibited by at least 70% by p-chloro-mercuribenzoic acid or sodium dodecylsulfate, but is not inhibited by o-phenanthroline or potassium ferricyanide; (9) Influence of metal salts: The enzyme is negligibly affected by Ni.sup.2+, Ba.sup.2+,Zn.sup.2+, Cd.sup.2+ or Mn.sup.2+ ; is inhibited by Fe.sup.3+ ; and loses activity in the presence of Hg.sup.2+ or Ag.sup.2+ ; and (10) Molecular Weight: About 95,500 (measured by SDS electrophoresis).

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