31] Properties of animal ceramide glycanases

Abstract

Ceramide glycanase (CGase), the endoglycosidase that cleaves various glycosphingolipids in a one-step process liberating ceramide and the corresponding oligosaccharides, is characterized from different annelids, bacteria, and mollusk. The same CGase activity has also been detected and purified from mammalian sources. The discovery of the mammalian CGases raises the possibility of glycosphingolipids (GSLs) being involved in the signal transduction and/or apoptotic processes as a secondary messenger. The ceramide and its breakdown product sphingosine that is very much in the limelight of apoptosis and signal transduction cascades have so far been predicted to come from the breakdown of the major membrane lipid sphingomyelin by the action of sphingomyelinase. Substantial CGase activities have been observed in different mammalian organs, although the highest activity was found in the mammary tissues. A parallel between CGase activity and the gestation as well as lactation has also been observed. However, the significance of this observation has not been established as it was for bovine mammary glucosidase. CGase activities in the kidneys and the mammary tissues of newborn rats parallel that found in the lactating mammary tissue. This chapter discusses the study of CGase characterized from mammalian sources.