PubMed Health⌕ Search

Biomedical subjects

C L Stults

Publications and source records attributed to C L Stults.

14 recordsLinked to original sources
PubMed1999

Characterization of the substrate specificity of alpha1,3galactosyltransferase utilizing modified N-acetyllactosamine disaccharides.

alpha1,3galactosyltransferase (alpha1,3GalT) catalyzes the synthesis of a range of glycoconjugates containing the Galalpha1,3Gal epitope which is recognized by the naturally occurring human antibody, anti-Gal. This enzyme may be a useful synthetic tool to produce a range of compounds to further investigate the binding site of anti-Gal and other proteins with a Galalpha1,3Gal binding site. Thus, the enzyme has been probed with a series of type 2 disaccharide-C8(Galbeta1-4GlcNAc-C8) analogs. The enzyme tolerated acceptors with modifications at C2 and C3 of the N-acetylglucosamine residue, producing a family of compounds with a nonreducing alpha1,3 linked galactose. Compounds that did not serve as acceptors were evaluated as inhibitors. Interestingly, the type 1 disaccharide-C8, Galbeta1-3GlcNAc-C8, was a good inhibitor of the enzyme (Ki = 270 microM vs. Km = 190 microM for Galbeta1-4GlcNAc-C8). A potential photoprobe, based on a modified type 2 disaccharide (octyl 3-amino-3-deoxy-3-N-(2-diazo-3, 3, 3-trifluoropropionyl-beta-D-galactopyranosyl-(1, 4)-2-acetamindo-2-deoxy-beta-D-glycopyranoside, (DTFP-LacNAc-C8)), was evaluated as an inhibitor of alpha1,3GalT. alpha1,3GalT bound DTFP-LacNAc-C8 with an affinity (Ki = 300 microM) similar to that displayed by the enzyme for LacNAc-C8. Additional studies were done to determine the enzyme's ability to transfer a range of sugars from UDP-sugar donors. The results of these experiments demonstrated that alpha1,3GalT has a strict specificity for UDP-Gal. Finally, inactivation studies with various amino acid modifiers were done to obtain information on the importance of different types of amino acids for alpha1,3GalT activity.

Amino Sugars↗
PubMed1995

Methyl 3-amino-3-deoxy-beta-D-galactopyranosyl-(1-->4)-2-acetamido-2- deoxy-beta-D-glucopyranoside: an inhibitor of UDP-D-galactose: beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D-glucose (1-->3)-alpha-D-galactopyranosyltransferase.

UDP-D-galactose:beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D- glucose alpha-(1-->3)-D-galactopyranosyltransferase [E.C. 2.4.1.151] transfers D-galactosyl-residues from the sugar nucleotide with retention of configuration. We report here that synthetic methyl 3'-amino-3'-deoxy-N-acetyllactosaminide (9), where the hydroxyl group normally undergoing galactosylation has been replaced by amino group, is an inhibitor for this enzyme with Ki = 104 microM. The mode of inhibition is not competitive, but appears to be specific, since other glycosyltransferases were not affected by 9.

Amino Sugars↗
PubMed1995

Alpha 1,4galactosyltransferase activity and Gb3Cer expression in human leukaemia/lymphoma cell lines.

We have used two methods to evaluate the level of expression of Gb3Cer in several human leukaemia/lymphoma cell lines representative of the myeloid (K562, KG-1, HL-60, and lymphoid (Reh, Daudi, Raji, RPMI 8226, CCRF-CEM, MOLT-4) lineages blocked at varied stages of differentiation. TLC immunostaining of glycolipid extracts with a monoclonal antibody, 12-101, and FACS analysis with the same antibody were used to demonstrate that the expression of Gb3Cer in neoplastic myeloid and lymphoid cells is both lineage and differentiation dependent. As a possible control point in the regulated expression of Gb3Cer we have investigated the first committed step in the synthesis of globo series glycosphingolipids that involves UDP-Gal:LacCer alpha (1,4)-galactosyltransferase (alpha 1,4GalT). We present the first characterization of this enzyme in a human myeloid cell line using an ELISA-based assay, which was subsequently used to measure alpha 1,4GalT activity in the human leukaemia/lymphoma cell lines. In general, there is a positive correlation between the levels of endogenous Gb3Cer and the level of the alpha 1,4 GalT activity. However, in two cases (KG-1 and CCRF-CEM) the level of enzyme activity did not correspond to the level of Gb3Cer expression.

Carbohydrate Conformation↗
PubMed1994

Analysis of glycosphingolipid glycosyltransferase products on TLC plates by combined storage phosphor and immunostaining techniques.

Measurement of glycosyltransferase activity in whole cell extracts is often complicated by the fact that several enzymes in an homogenate are capable of using the same nucleotide sugar donor, thereby generating a range of products from both an exogenous and any endogenous acceptors. We report the use of a novel combination of techniques to simultaneously identify and quantify the products generated from a whole cell extract in a single experiment. Several radiolabeled glycosphingolipid products were generated by the addition of UDP-[14C]Gal to a reaction mixture containing an homogenate from a human leukemia cell line, THP-1. After the 14C-labeled products were separated on a TLC plate, storage phosphor technology and immunostaining (with carbohydrate sequence-specific monoclonal antibodies) were used sequentially on the same plate to simultaneously identify and quantify each of the glycosyltransferase products. This method allows product identification and quantification in the femtomole range. Thus, low levels of endogenous acceptors were easily detected. We have used a similar method with UDP-[3H]Gal to obtain glycosyltransferase product profiles from several human leukemia/lymphoma cell lines and subsequently identify two galactosyltransferase activities in these cell lines: UDP-Gal:Gal beta 1-4Glc beta 1-1Cer alpha 1,4galactosyltransferase; and UDP-Gal:GlcNAc beta 1--3Gal beta 1--4Glc beta 1--1Cer beta 1,4galactosyltransferase. In addition to product characterization, this method was used with reaction mixtures at different pH to demonstrate the usefulness of the method for characterizing multiple enzyme activities simultaneously.

Antibodies, Monoclonal↗
PubMed1994

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)

Carbohydrate Sequence↗
PubMed1994

Expression of fucosylated antigens and alpha 1,3 fucosyltransferases in human leukaemia cell lines.

The expression of alpha 1,3 fucosylated type 2 antigens is generally thought to be restricted to myeloid cells among normal human haemopoietic tissue. The distribution of three fucosylated antigens [Lewis X (Le(x)), sialyl Lewis X (sLex) and VIM2] was investigated among nine human leukaemia cell lines by fluorescence activated cell sorting (FACS) analysis. As expected, all myeloid cell lines were positively stained by antibodies against these three fucosylated antigens. Unexpectedly, two T-lymphocytic cell lines (CCRF-CEM and MOLT4) were found to express Le(x) and VIM2, and the plasma, B-cell line, RPMI 8226, expressed all three fucosylated antigens. Enzymatic and RNA analyses [Northern blot and reverse transcription polymerase chain reaction (RT-PCR)] were used to evaluate possible control points in the biosynthetic pathway for Le(x) and sLex. beta 1,4 Galactosyltransferase (beta 1,4GalT, an enzyme involved in the synthesis of the core oligosaccharide of the three fucosylated antigens) activity and the corresponding mRNA were found in all of the leukaemia cell lines, regardless of whether or not they expressed the fucosylated antigens. In contrast, alpha 1,3 fucosyltransferase (GDP-fucose:beta-D-N-acetylglucosaminide 3-alpha-L-fucosyltransferase; alpha 1,3FT) activity and the corresponding mRNA were found only in those cell lines expressing fucosylated antigens. Based on RNA analysis, acceptor specificity and N-ethylmaleimide inhibition studies, it was concluded that all of the cell lines expressing fucosylated antigens contained alpha 1,3FTIV (myeloid alpha 1,3FT). This appeared to be the major alpha 1,3FT in the myeloid and T-lymphocytic cell lines. Interestingly, even though both types of cell lines expressed the same alpha 1,3FT, only the myeloid cell lines expressed sLex, whereas all of the myeloid and T-lymphocytic cell lines expressed a structural analogue of sLex (i.e. VIM2). In contrast to the myeloid and T-cell lines, RPMI 8226 cells contained more than one fucosyltransferase activity. Acceptor specificity analysis demonstrated that this cell line contains alpha 1,3 and alpha 1,4FTs. Among the fucosyltransferases expressed by RPMI 8226, alpha 1,3FTIV accounted for only a small amount of the total activity. The results of this study demonstrate that fucosylated antigens, which are generally considered to be myeloid specific antigens, are also expressed by lymphocytic leukaemia cell lines, and that the types of fucosylated antigens and fucosyltransferases expressed in these cell lines vary.

Antigens, Neoplasm↗
PubMed1993

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

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.

Carbohydrate Sequence↗
PubMed1990

Regulation of the expression of Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids in kidney.

Previous studies (Galili, U., Clark, M. R., Shohet, S. B., Buehler, J., and Macher, B. A. (1987) Proc. Natl. Acad. Sci. U. S. A. 84, 1369-1373; Galili, U., Shohet, S. B., Korbrin, E., Stults, C. L. M., and Macher, B. A. (1988) J. Biol. Chem. 263, 17755-17762) have established that there is a unique evolutionary distribution of glycoconjugates carrying the Gal alpha 1-3Gal beta 1-4GlcNAc epitope. These glycoconjugates are expressed by cells from New World monkeys and non-primate mammals, but not by cells from humans, Old World monkeys, or apes. The lack of expression of this epitope in the latter species appears to result from the suppression of gene expression for the enzyme UDP-galactose:nLc4Cer alpha 1-3-galactosyltransferase (alpha 1-3GalT) (Joziasse, D. H., Shaper, J. H., Van den Eijnden, D. H., Van Tunen, A. J., and Shaper, N. L. (1989) J. Biol. Chem. 264, 14290-14297). Although many non-primate species are known to express this carbohydrate epitope, the nature (i.e. glycoprotein or glycosphingolipid) of the glycoconjugate carrying this epitope is only known for a few tissues in a few animal species. Furthermore, it is not known whether all animal species express this epitope in the same tissues. We have investigated these questions by analyzing the glycosphingolipids in kidney from several non-primate animal species. Immunostained thin layer chromatograms of glycosphingolipids from sheep, pig, rabbit, cow, and rat kidney with the Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipid-specific monoclonal antibody, Gal-13, demonstrated that kidney from all of these species except rat contained Gal alpha 1-3Gal beta 1-4GlcNAc neutral glycosphingolipids. A lack of expression of Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids in rat may be due to the lack of expression of the enzyme (alpha 1-3GalT) which catalyzes the formation of the Gal alpha 1-3Gal nonreducing terminal sequence of these compounds or to the lack of expression of glycosyltransferases which are necessary for the synthesis of the neolacto core structure of these compounds. These possibilities were evaluated in two ways. First, the three enzymes (UDP-N-acetylglucosamine:LacCer beta 1-3-N-acetyl-glucosaminyltransferase, UDP-galactose:Lc3Cer beta 1-4-galactosyltransferase, and alpha 1-3GalT) involved in the synthesis of the Gal alpha 1-3Gal beta 1-4GlcNAc glycosphingolipids were assayed using an enzyme-linked immunosorbent assay-based assay system and carbohydrate sequence-specific monoclonal antibodies. Second, TLC immunostaining was done to determine if the glycosphingolipid precursors (i.e. Lc3Cer and nLc4Cer) are expressed in rat kidney. Interestingly, rat kidney had a relatively high level of alpha 1-3GalT activity compared with the other animals tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Measurement of beta-galactosyltransferase activity in cell extracts with an ELISA-based assay.

An enzyme-linked immunosorbent assay (ELISA)-based glycosyltransferase assay has been used to measure UDP-Gal:N-acetylglucosamine beta-1,4-galactosyl-transferase (EC 2.4.1.38) activity in detergent extracts of chinese hamster ovary (CHO) cells. LEC11 cells (a mutant of the CHO cell line, Pro -5), which are known to express a complex array of carbohydrate structures, were used to develop the assay for use with whole cell extracts. A detergent-solubilized preparation of the enzyme from whole cells was used to convert the substrate, lactotriglycosylceramide, to the product, neolactotetraglycosylceramide. The monoclonal antibody, 1B2, which specifically binds to the Gal beta 1-4GlcNAc epitope, was used in an ELISA to identify and quantify the product. The enzyme activity in the preparations was found to be similar to that obtained by conventional radioactive assay methods. The beta-galactosyltransferase found in LEC11 cell detergent extracts exhibited an absolute requirement for the nucleotide sugar and MnCl2. The activity of the enzyme was also strictly dependent on the presence of exogenous glycolipid acceptor. When Triton X-114 was used to solubilize the LEC11 beta-galactosyltransferase, activity was found in both the hydrophilic and the hydrophobic phases, suggesting the presence of two forms of the enzyme. The ELISA-based assay was used to compare beta-1,4-galactosyltransferase activity in detergent extracts of four CHO cell lines: Pro-5, Lec1, LEC11, and LEC12 and in detergent-solubilized microsomes from human leukemia cells. The results from this study demonstrate the utility of the ELISA-based assay for measuring glycosyltransferase activity in detergent-solubilized whole cells and microsome preparations.

Animals↗
PubMed1988

Man, apes, and Old World monkeys differ from other mammals in the expression of alpha-galactosyl epitopes on nucleated cells.

The study of the expression of alpha-galactosyl epitopes on various mammalian cells is of particular interest, since as much as 1% of circulating IgG antibodies in humans interact with this carbohydrate residue. This natural antibody, designated "anti-Gal," was previously found to bind to terminal Gal alpha 1----3Gal beta 1----4GlcNAc-R on biochemically defined glycolipids (Galili, U., Macher, B. A., Buehler, J., and Shohet, S. B. (1985) J. Exp. Med. 162, 573-582; Galili, U., Buehler, J., Shohet, S. B., and Macher, B. A. (1987) J. Exp. Med. 165, 693-704). The expression of anti-Gal binding epitopes on nucleated cells from various mammalian species was studied by immunostaining with this antibody. The binding of anti-Gal to various cells was correlated with the binding of the lectin Bandeiraea (Griffonia) simplicifolia IB4 (BS lectin). The BS lectin also interacts with alpha-galactosyl residues and particularly with high affinity with Gal alpha 1----3Gal beta 1----4GlcNAc residues. We observed a striking evolutionary pattern in the expression of these epitopes on mammalian nucleated cells. Fibroblasts, epithelial cells, endothelial cells, smooth muscle cells, and lymphoid cells of nonprimate mammals, prosimians, and New World monkeys readily bound both anti-Gal and BS lectin. However, no such binding was detectable on cells of Old World monkeys, apes, and humans. Measurment of the binding of radiolabeled BS lectin to the various nucleated cells suggests that cells binding anti-Gal express 10(6) to 3.5 x 10(7) alpha-galactosyl epitopes, most of which, based on the anti-Gal specificity, seem to have the structure of Gal alpha 1----3Gal beta 1----4GlcNAc-R. The absence of these epitopes from human cells results from diminished activity of the enzyme alpha 1----3 galactosyltransferase, which catalyzes the following reaction. Gal beta 1----4GlcNAc-R + UDP-Gal(alpha 1----3-galactosyltransferase)----Gal alpha 1----3Gal beta 1----4GlcNAc-R + UDP This enzyme, which participates in the glycosylation of cell membrane glycoconjugates in nonprimate mammals, prosimians, and New World monkeys, appears to have been suppressed in Old World primates as a result of evolutionary events which occurred 20-30 million years ago. It is argued that an anomalous activity of this enzyme in man may result in initiation of autoimmune diseases because of the de novo expression of Gal alpha 1----3Gal beta 1----4GlcNAc-R epitopes recognized by anti-Gal.

ABO Blood-Group System↗
PubMed1988

Enzyme-linked immunosorbent assay (ELISA)-based quantification and identification of in vitro enzyme-catalyzed glycosphingolipid synthesis and degradation products with carbohydrate sequence-specific monoclonal antibodies.

A new method has been developed to monitor glycosyltransferase and glycosylhydrolase activities. Reaction product identification and quantification are accomplished simultaneously with an enzyme-linked immunosorbent assay (ELISA) using carbohydrate sequence-specific monoclonal antibodies. beta-Galactosyltransferase and alpha-galactosidase reactions were used to illustrate the salient features of the method. These include simple product identification and quantification, no detergent requirement, consumption of small amounts of reagents, and no use of radioisotopes. Furthermore, it is possible to measure substrate disappearance or product formation with this method. Enzyme characteristics such as Km, Vmax, divalent cation requirement, and pH optimum were investigated with this new method.

Animals↗