Characteristics of β-galactosidase in the mucosa of the small intestine of infant rats. Physicochemical properties

Abstract

1. The characteristics of acid and neutral β-galactosidases isolated chromatographically from homogenates of the mucosa of the jejunum and ileum of suckling rats were studied. 2. The minimal molecular weight of the acid β-galactosidase, as estimated by gel filtration on Sephadex G-200, was in the range 83000–105000, whereas for the neutral β-galactosidase the estimated molecular weight was in the range 360000–510000. 3. The acid and neutral β-galactosidases were inhibited competitively by galactono-(1→4)-lactone, with respective Ki values of 0·15mm and 1·1mm. Only the acid β-galactosidase was inhibited competitively by sodium galactonate (Ki 0·17mm). 4. Heat inactivation of both β-galactosidases occurred according to first-order kinetics. The neutral enzyme was more labile, but bovine serum albumin protected acid enzyme only. 5. Urea treatment inactivated both β-galactosidases, the neutral β-galactosidase being more sensitive than the acid β-galactosidase. 6. No differences were found between preparations from the jejunum and ileum.