Exhibited similar substrate specificity to wild-type. The distance between the residue and the catalytic pocket was too far to enable the binding or positioning of a water molecule for hydrolysis activity. On the other hand,and M375I (increased hydrophobicity), which was also located between the third and the fourth conserve region,affected hydrolysis active severely. as shown by a reduction in specific activity. The M375I residue is located close to the active site and was positioned at the entrance path of the water molecule. The improved substrate specificity of M375I toward soluble starch, amylose and amylopectin was due to the fact that the substitution of Met with a smaller amino acid led to the reduction of steric interference