1. The p-nitrophenyl β-D-galactosidase asctivity in rat liver homogenates of lysosome-rich fractions was shown to be markedly affected by the ionic composition of the medium. A stimulation of the reaction rate at pH 5 was produced by most of the salts tested, which contained anions such as acetate, SO42− and Cl−, and cations such as Na+, K+ and Mg2+. The most pronounced effect was observed with MgCl2. Only potassium glutamate was inhibitory. 2. Five peaks of β-galactosidase activity obtained by DEAE-cellulose chromatography were equally sensitive to changes in the ionic composition of the medium. In the presence of added NaC1, the whole rate-pH curve was displaced towards higher pH values, the optimum being shifted from 2.0-2.5 to 3.5. The stimulation at pH 5.0 appeared to be mainly due to changes in Vmax., whereas the apparent Km was slightly modified. 3. Unlike the total, the free β-galactosidase activity remained unchanged or even declined when KC1 was added to the reaction medium.
Research Article|December 01 1975
Stimulation of rat liver β-galactosidase activity by ions
F M Baccino;
M F Zuretti;
Biochem J (1975) 151 (3): 567-573.
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F M Baccino, M F Zuretti, L Pernigotti; Stimulation of rat liver β-galactosidase activity by ions. Biochem J 1 December 1975; 151 (3): 567–573. doi: https://doi.org/10.1042/bj1510567
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