Abstract:
Glycosphingolipids (GSLs) have been implicated as playing major roles in cellular interactions and control of cell proliferation
in muticellular organisms. Moreover GSLs and other sphingolipids such as sphingomyelins, ceramides and sphingosines serve a
variety of roles in signal transduction. Hence, identification of structures of GSLs in different biota will shed light in understanding
their physiological role. During this study, the major glycosphingolipid component present in the extracts of stage-12 and stage-17/18
metamorphosing adults of Manduca sexta was identified as mactosyl ceramide. We report the isolation of several ceramide
disaccharides, a ceramide trisaccharide and a ceramide tetrasaccharide. The GSL structures were confirmed by high-resolution
mass spectrometry and tandem mass spectrometry. The identity of the monosaccharides was proved using exoglycosidases.
The predominant sphingosine chain-length varied from C-14 (tetradecasphing-4-enine) to C-16 (hexadecasphing-4-enine) in these
GSLs. Sphingosines of both chain lengths were accompanied by their doubly unsaturated counterparts tetradecasphinga-4,6-diene
and hexadecasphinga-4,6-diene. It is also interesting to note the presence of tetradecasphinganine and hexadecasphinganine in
minute amounts in the form of a GSL in the extracts of M. sexta. The varying degrees of unsaturation in the sphingosine moiety of
GSLs in M. sexta may be biologically significant in insect metamorphosis. The ceramide trisaccharides and ceramide tetrasaccharide
belong to the arthro-series, The observation of fucose in the M. sexta GSLs is the first report of the presence of fucose in an
arthroseries GSL.
Graphical abstract
