The Role of a Tyrosine Residue of Bacterial Liquefying α-Amylase^* in the Enzymatic Hydrolysis of Linear Substrates as Studied by Chemical Modification with Acetic Anhydride

抄録

A tyrosine residue of liquefying α-amylase [EC 3. 2. 1. 1] from B. subtilis was acetylated with acetic anhydride and the effect of the modification on the rate of enzyme reaction was studied with a series of maltooligosaccharides. It was found that the acetylation of a tyrosine residue leads to partial loss of enzyme activity and that the effect does not depend appreciably on the degree of polymerization (n) of the linear substrates in the range n=3_??_7 and 760. The results are consistent with the supposition that the modified tyrosine residue is located at a subsite near the catalytic site and is involved in the productive binding of all the substrates studied.