Cerebroside galactosidase of brain

Abstract

The galactoside bond in cerebroside was found to be cleaved by an enzyme in rat and pig brain. Emulsified stearoyl-(14)C psychosine was used as the substrate and the extent of cleavage was studied by isolating and counting the stearoyl sphingosine (ceramide) formed. The reaction products, ceramide and galactose, were characterized by column and thin-layer chromatography. Cerebroside containing galactose-(3)H was also used to show liberation of galactose. Cholic acid was found to be required for activation of the enzyme, which has a pH optimum of 4.5. Similar cerebrosidase activity was found in spleen, kidney, and lung of rat; liver and heart showed very slight activity. The partially purified enzyme from pig brain also formed ceramide from ceramide lactoside, ceramide glucoside, and cerebronoyl psychosine. The enzyme was active toward o-nitrophenyl galactoside and could be fractionated by Sephadex chromatography into a fraction active toward the nitrophenyl galactoside only and a fraction active toward both this substrate and ceramide galactoside. Human spleen, normal and Gaucher, exhibited cerebrosidase activity.