Structure and Function of Xanthomonas campestris alpha-amylase

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This study aimed to get further structure / function relationship of Xanthomonas campestris alpha-amylase and three results as below were obtained.1. Mutant enzymes of which the 6th loop in (alpha / beta) 8 barrel was shortened by 4,8, or 12 amino acid residues were created. The selectivity of enzymes toward glycogen increased fivefold and twentyfold in the case of 4 and 8 residues-deleted mutant enzyme, respectively. This suggests that the long 6th loop of X.campestris alpha-amylase caused the steric hindrance between enzyme and glycogen. It is possible to say that a new enzyme can be created by partial deletion of loop in alpha-amylase,2. X.campestris alpha-amylase was crystallized by the hanging drop method. Conditions were as follows ; enzyme concentration, 10 mg / ml ; pH 4.5 ; temperature, 20ﾟC ; precipitant in reservoir and drop, 15% and 10%, respectively, saturated ammonium sulfate in 10 mM sodium acetate (pH 4.5).3. Auto-oxidation of methionine 82 was suspected to be a reason for the inactivation of X.campestris alpha-amylase, thus, the residue was replaced by alanine. The mutant enzyme was found to be quite stable in the presence of oxidizer of high concentration.