Stimulation of rat liver beta-galactosidase activity by ions.
1.  The p-nitrophenyl beta-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, SO4(2-) 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 beta-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 beta-galactosidase activity remained unchanged or even declined when KC1 was added to the reaction medium.
D000085:Acetates; D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D002729:Chloromercuribenzoates; D002848:Chromatography, DEAE-Cellulose; D004789:Enzyme Activation; D005696:Galactosidases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D005971:Glutamates; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000494:pharmacology*; D008099:Liver / Q000032:analysis / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology
D000085:Acetates; D002712:Chlorides; D002729:Chloromercuribenzoates; D005971:Glutamates; D007477:Ions; D012964:Sodium; D005696:Galactosidases; D008274:Magnesium; D011188:Potassium