Structural characterization of intermediates in the biosynthetic pathway of neolacto glycosphingolipids: differential expression in human leukaemia cells.
The biosynthesis of neolacto glycosphingolipids is thought to proceed via reactions catalysed by the two enzymes beta 1-3-N-acetylglucosaminyltransferase (beta 1,3GlcNAcT) and beta 1-4 galactosyltransferase (beta 1,4GalT). In general, only the products of the latter enzyme have been isolated from tissues and structurally characterized. Among the GlcNAc beta 1-3-R glycosphingolipids, only lactotrioasylceramide (Lc3Cer, the initial product in the biosynthesis of neolacto glycosphingolipids) has been isolated and structurally characterized. Longer-chain glycosphingolipids with a terminal GlcNAc-beta 1-3-R structure are considered to be intermediates in the synthesis of complex neolacto glycosphingolipids. We have detected a series of GlcNAc beta 1-3-R glycosphingolipids in extracts obtained from human leukocytes isolated from patients with leukaemia using a monoclonal antibody (TE5) which specifically recognizes these compounds. The structures of three of these compounds purified from chronic myelocytic leukaemia (CML) cells have been determined using a combination of enzymatic, immunostaining and chemical methods. The compounds were found to have the following structures: GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer (Lc3Cer) GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer (nLc5Cer) GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer (nLc7Cer) A longer-chain compound, apparently nLc9Cer, was also detected. TLC immunostaining analysis of glycosphingolipids isolated from cells obtained from patients with various leukaemias demonstrated that GlcNAc beta 1-3-R glycosphingolipids have a distribution that depends on the stage of differentiation and lineage of the cell population.(ABSTRACT TRUNCATED AT 250 WORDS)
Hu
J
J
Department of Chemistry and Biochemistry, San Francisco State University, CA 94132.
Stults
C L
CL
Holmes
E H
EH
Macher
B A
BA
D002240:Carbohydrate Sequence; D002454:Cell Differentiation; D005700:Galactosyltransferases / Q000378:metabolism; D006028:Glycosphingolipids / Q000096:biosynthesis* / Q000302:isolation & purification; D006801:Humans; D007938:Leukemia / Q000378:metabolism*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism; D015479:Leukemia, Myelomonocytic, Acute / Q000378:metabolism; D008745:Methylation; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism; D014407:Tumor Cells, Cultured
D006028:Glycosphingolipids; D005700:Galactosyltransferases; D017351:N-Acetylglucosaminyltransferases