STUDIES ON SUBSTRATE SPECIFICITY OF TAKA-AMYLASE A .2. MODE OF ACTION OF TAKA-AMYLASE A ON O-METHYL DERIVATIVES OF PHENYL ALPHA-MALTOSIDE

Several specimens of a mixture of partially O-methylated derivatives of phenyl α-maltoside were prepared where O-methylated glucose residues were predominantly mono-O-methyl derivative. The enzymatic action of Taka-amylase A [EC 3. 2. 1. 1] on these specimens was investigated, and the reaction products were detected. Among the reaction products, the following maltose derivatives were identified: 3'-O-methyl-maltose, 4'-O-methyl-maltose, 6'-O-methyl-maltose, and 4', 6'-di-O-methyl-maltose. Any maltose derivative which had O-methyl substituent on the reducing end glucose residue was never produced by the enzyme. Phenyl 2'-O-methyl-α-maltoside which was inferred to be present in a specimen, was found to be resistant to the enzymatic action. Consequently, it seemed that in the maltose moiety of a substrate molecule all the hydroxyls on the reducing end glucose residue and the 2-hydroxyl on the non-reducing end residue played important roles in the enzymatic reaction. © 1969 BY THE JOURNAL OF BIOCHEMISTRY.