Rabbit small intestinal beta-galactosidases.

The beta-galactosidase activities of the rabbit small intestinal mucosa were studied over the pH range of 2.6 to 8.4, using different substrates, and in the presence or absence of the enzyme inhibitor p-chloromercuribenzoic acid. The results indicated the presence of 4 beta-galactosidases: (i) a neutral beta-galactosidase (lactase) with optimum pH of 5.8, (ii) an acid beta-galactosidase I with optimum pH of 3.4, (iii) an acid beta-galactosidase II with optimum pH of 4.6, and (iv) a hetero beta-galactosidase with pH optimum of 7.6. Seemingly, 3 of these beta-galactosidases were comparable with those in other mammals, and the 4th has not been reported in other species.