1972 年 92 巻 1 号 p. 64-68
Hen egg white lysozyme was acetylated with acetic anhydride, the acetylated lysozyme was fractionated by CM-cellulose column chromatography, and four main peaks termed FI, FII, FIII, and FIV were obtained. The properties of FI, FII, and FIII were the same as described in the previous paper, while FIV possessed about 6 unmodified amino groups per molecule and retained 33% of the relative activity of M. lysodeikticus as compared with native lysozyme. Physicochemical properties, i.e., optical rotatory dispersion, pH titration of tyrosine, and differential spectrum of the enzyme by glycol chitin were investigated. Helical contents decreased about 5%, and buried tyrosine was easily titrated by spectrophotometry, and the difference in spectrum at 293 nm of the enzyme-substrate complex had a lower value in FII and FIII, but FIV exhibited 122% relative activity of the lysozyme. Quantitative precipitin reaction and immunodiffusion revealed that the antigenic determinants decreased by chemical modification. From the previous results, it might be concluded that FIV has lost the antigenic determinant though it retained the nature of a native lysozyme.