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Beta 1-3-N-acetylglucosaminyltransferase in human leukocytes: properties and role in regulating neolacto glycosphingolipid biosynthesis. 1993

C L Stults, and B A Macher
Department of Chemistry and Biochemistry, San Francisco State University, California 94132.

There are well-established differences in the expression of neolacto neutral glycosphingolipids among human leukocyte subclasses. Mature myeloid cells express several types of these compounds, whereas mature lymphoid cells are deficient in such compounds. The biochemical basis for this is unknown. Therefore, enzyme studies were done to determine whether different classes of leukocytes (represented by cell lines) contained beta 1-3-N-acetylglucosaminyltransferase activity (EC 2.4.1.149, beta 1-3GlcNAcT(i)). This enzyme participates in the synthesis of Type 2 chains in glycosphingolipids by catalyzing the following two reactions: (i) Gal beta 1-4Glc beta 1-1Cer (lactosylceramide, LacCer) + UDP-GlcNAc-->GlcNAc beta 1-3Gal beta 1-4Glc beta 1- 1Cer (lactotriaosylceramide) and (ii) Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer (neolactotetraosylceramide) + UDP-GlcNAc-->GlcNAc beta 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1Cer. The first reaction may be the key step in the biosynthetic pathway of neolacto structures in human leukocytes. Therefore, extracts from several cell lines representative of both myeloid and lymphoid lineages, at varied stages of maturity, were assayed with LacCer for the presence of beta 1-3GlcNAcT(i) activity. Our results indicate that myeloid cells contain this initiating beta 1-3GlcNAcT(i) activity, whereas lymphoid cells do not. This is consistent with our thin-layer chromatography immunostain results which show that all myeloid cell lines express neutral neolacto glycosphingolipids and lymphoid cells do not. Our findings suggest that the presence of the initiating activity only in myeloid cells is a regulatory factor in the expression of neutral neolacto glycosphingolipids in human leukocytes. We also tested both myeloid and lymphoid cell lines for the presence of elongating beta 1-3GlcNAcT(i) activity (reaction (ii) above) by using neolactotetraosylceramide as an acceptor. Our results show that an elongating activity is expressed by all myeloid and lymphoid cell lines tested. Initiating (myeloid) and elongating (myeloid and lymphoid) activities were distinguished by several characteristics: metal ion activation, pH optimum, and kinetic constants. In conclusion, our results indicate the presence of two beta 1-3GlcNAcT(i) activities in human leukocytes: one that catalyzes the initial reaction and is found only in the myeloid lineage and one that catalyzes the elongating reaction and is found in both myeloid and lymphoid cells.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D007962 Leukocytes White blood cells. These include granular leukocytes (BASOPHILS; EOSINOPHILS; and NEUTROPHILS) as well as non-granular leukocytes (LYMPHOCYTES and MONOCYTES). Blood Cells, White,Blood Corpuscles, White,White Blood Cells,White Blood Corpuscles,Blood Cell, White,Blood Corpuscle, White,Corpuscle, White Blood,Corpuscles, White Blood,Leukocyte,White Blood Cell,White Blood Corpuscle
D008969 Molecular Sequence Data Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories. Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D002240 Carbohydrate Sequence The sequence of carbohydrates within POLYSACCHARIDES; GLYCOPROTEINS; and GLYCOLIPIDS. Carbohydrate Sequences,Sequence, Carbohydrate,Sequences, Carbohydrate
D002413 Cations, Divalent Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis. Divalent Cations
D002454 Cell Differentiation Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs. Differentiation, Cell,Cell Differentiations,Differentiations, Cell
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D006028 Glycosphingolipids Lipids containing at least one monosaccharide residue and either a sphingoid or a ceramide (CERAMIDES). They are subdivided into NEUTRAL GLYCOSPHINGOLIPIDS comprising monoglycosyl- and oligoglycosylsphingoids and monoglycosyl- and oligoglycosylceramides; and ACIDIC GLYCOSPHINGOLIPIDS which comprises sialosylglycosylsphingolipids (GANGLIOSIDES); SULFOGLYCOSPHINGOLIPIDS (formerly known as sulfatides), glycuronoglycosphingolipids, and phospho- and phosphonoglycosphingolipids. (From IUPAC's webpage) Asialoganglioside,Asialogangliosides,Glycosphingolipid,Sphingoglycolipid,Sphingoglycolipids
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations

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