A taurodeoxycholate-activated galactosylceramidase in the murine intestine

Highly active enzymatic hydrolysis of galactosylceramide was detected in the murine intestine in confirmation of an earlier report in the rat intestine (Brady, R. O., Gal, A. E., Kanfer, J. N., and Bradley, R. M. (1965) J. Biol. Chem. 240, 3766-3770). Unlike the classical galactosylceramidase (EC 3.2.1.46), which is present in other organs, as well as also in the intestine, this intestinal enzyme was not activated by sodium taurocholate and was inhibited by oleic acid. It was effectively activated by sodium taurodeoxycholate and had a pH optimum of 5.2. This taurodeoxycholate-activated galactosylceramidase did not appear to be present in the brain, liver, kidney, and spleen. Its activity was not deficient in affected twitcher mice, a newly discovered mutant caused by a genetic deficiency of the taurocholate-activated galactosylceramidase. Although it showed a relatively neutral pH optimum, the taurodeoxycholate-activated galactosylceramidase is not a nonlysosomal "neutral" beta-galactosidase, because unlike the latter, it was adsorbed to Concanavalin A-Sepharose after solubilization with 0.5% sodium taurodeoxycholate and was eluted by alpha-methylmannoside or alpha-methylglucoside. The taurodeoxycholate-activated galactosylceramidase could be completely separated from the taurocholate-activated galactosylceramidase and GM1-ganglioside beta-galactosidase (EC 3.2.1.23) by octyl-Sepharose hydrophobic chromatography. Thus, the taurodeoxycholate-activated galactosylceramidase localized in the intestine is distinct from the two known glycosphingolipid beta-galactosidases and the neutral beta-galactosidase.