Anup Kumar Misra

The α(1,3)fucosyltransferases FucT-IV and FucT-VII Exert Collaborative Control over Selectin-Dependent Leukocyte Recruitment and Lymphocyte Homing

E-, P-, and L-selectin counterreceptor activities, leukocyte trafficking, and lymphocyte homing are controlled prominently but incompletely by alpha(1,3)fucosyltransferase FucT-VII-dependent fucosylation. Molecular determinants for FucT-VII-independent leukocyte trafficking are not defined, and evidence for contributions by or requirements for other FucTs in leukocyte recruitment is contradictory and incomplete. We show here that inflammation-dependent leukocyte recruitment retained in FucT-VII deficiency is extinguished in FucT-IV(-/-)/FucT-VII(-/-) mice. Double deficiency yields an extreme leukocytosis characterized by decreased neutrophil turnover and increased neutrophil production. FucT-IV also contributes to HEV-born L-selectin ligands, since lymphocyte homing retained in FucT-VII(-/-) mice is revoked in FucT-IV(-/-)/FucT-VII(-/-) mice. These observations reveal essential FucT-IV-dependent contributions to E-, P-, and L-selectin ligand synthesis and to the control of leukocyte recruitment and lymphocyte homing.

Poly-N-acetyllactosamine Extension inN-Glycans and Core 2- and Core 4-branchedO-Glycans Is Differentially Controlled by i-Extension Enzyme and Different Members of the β1,4-Galactosyltransferase Gene Family

Poly-N-acetyllactosamines are attached to N-glycans, O-glycans, and glycolipids and serve as underlying glycans that provide functional oligosaccharides such as sialyl LewisX. Poly-N-acetyllactosaminyl repeats are synthesized by the alternate addition of β1,3-linked GlcNAc and β1,4-linked Gal by i-extension enzyme (iGnT) and a member of the β1,4-galactosyltransferase (β4Gal-T) gene family. In the present study, we first found that poly-N-acetyllactosamines inN-glycans are most efficiently synthesized by β4Gal-TI and iGnT. We also found that iGnT acts less efficiently on acceptors containing increasing numbers of N-acetyllactosamine repeats, in contrast to β4Gal-TI, which exhibits no significant change. In O-glycan biosynthesis,N-acetyllactosamine extension of core 4 branches was found to be synthesized most efficiently by iGnT and β4Gal-TI, in contrast to core 2 branch synthesis, which requires iGnT and β4Gal-TIV. Poly-N-acetyllactosamine extension of core 4 branches is, however, less efficient than that of N-glycans or core 2 branches. Such inefficiency is apparently due to competition between a donor substrate and acceptor in both galactosylation andN-acetylglucosaminylation, since a core 4-branched acceptor contains both Gal and GlcNAc terminals. These results, taken together, indicate that poly-N-acetyllactosamine synthesis inN-glycans and core 2- and core 4-branchedO-glycans is achieved by iGnT and distinct members of the β4Gal-T gene family. The results also exemplify intricate interactions between acceptors and specific glycosyltransferases, which play important roles in how poly-N-acetyllactosamines are synthesized in different acceptor molecules.

Syntheses and evaluation of glucosyl aryl thiosemicarbazide and glucosyl thiosemicarbazone derivatives as antioxidant and anti-dyslipidemic agents

A series of N-per-O-acetyl-glucosyl arylthiosemicarbazide and thiosemicarbazone derivatives have been synthesized and evaluated for their in vivo anti-dyslipidemic and in vitro antioxidant activities. Among 16 compounds tested, 3 compounds showed potent anti-dyslipidemic activity and 6 compounds showed potent antioxidant and scavenger of oxygen free radicals activity.

Nitric acid mediated oxidative transformation of thiols to disulfides

Abstract Oxidation of thiols to disulfides are reported using nitric acid/methylene chloride. Environmentally benign, economically convenient and simple reaction condition represents an attractive alternative to the existing approaches on both the laboratory and the industrial scale. #C.D.R.I. Communication No: 6412.

Molecular Cloning and Expression of a Novel Human β-Gal-3-O-sulfotransferase That Acts Preferentially onN-Acetyllactosamine in N- andO-Glycans

A novel cDNA-encoding galactose 3-O-sulfotransferase was cloned by screening the expressed sequence tag data base using the previously cloned cDNA encoding a galactosyl ceramide 3-O-sulfotransferase, which we term Gal3ST-1. The newly isolated cDNA encodes a novel 3-O-sulfotransferase, termed Gal3ST-3, that acts exclusively on N-acetyllactosamine present inN-glycans and core2-branched O-glycans. These conclusions were confirmed by analyzing CD43 chimeric proteins in Chinese hamster ovary cells expressing core2 β1,6-N-acetylglucosaminyltransferase. The acceptor specificity of Gal3ST-3 contrasts with that of the recently cloned galactose 3-O-sulfotransferase (Honke, K., Tsuda, M., Koyota, S., Wada, Y., Iida-Tanaka, N., Ishizuka, I., Nakayama, J., and Taniguchi, N. (2001) J. Biol. Chem. 276, 267–274), which we term Gal3ST-2 in the present study because the latter enzyme can also act on core1 O-glycan and type 1 oligosaccharides, Galβ1→3GlcNAc. Moreover, Gal3ST-3 but not Gal3ST-2 can act on Galβ1→4(sulfo→6)GlcNAc, indicating that disulfated sulfo→3Galβ1→4(sulfo→6) GlcNAc→R may be formed by Gal3ST-3 in combination with GlcNAc 6-O-sulfotransferase. Although both Gal3ST-2 and Gal3ST-3 do not act on galactosyl ceramide, Gal3ST-3 is only moderately more homologous to Gal3ST-2 (40.1%) than to Gal3ST-1 (38.0%) at the amino acid level. Northern blot analysis demonstrated that transcripts for Gal3ST-3 are predominantly expressed in the brain, kidney, and thyroid where the presence of 3′-sulfation ofN-acetyllactosamine has been reported. These results indicate that the newly cloned Gal3ST-3 plays a critical role in 3′-sulfation of N-acetyllactosamine in both O- and N-glycans.

Removal of benzylidene acetal and benzyl ether in carbohydrate derivatives using triethylsilane and Pd/C.

Summary Clean deprotection of carbohydrate derivatives containing benzylidene acetals and benzyl ethers was achieved under catalytic transfer hydrogenation conditions by using a combination of triethylsilane and 10% Pd/C in CH3OH at room temperature. A variety of carbohydrate diol derivatives were prepared from their benzylidene derivatives in excellent yield.

Aza-Michael addition of amines to activated alkenes catalyzed by Silica supported perchloric acid under a solvent-free condition ¶

An efficient aza-Michael addition of amines to a series of α,β-unsaturated ketones, carboxylic esters, nitriles and chalcones has been carried out using perchloric acid supported over silica gel (HClO4-SiO2) at room temperature in high yields under solvent-free reaction conditions.

Significant rate accelerated synthesis of glycosyl azides and glycosyl 1,2,3-triazole conjugates

AbstractAn efficient and significantly rapid access of a series of glycosyl azides and glycosyl 1,2,3-triazole conjugates is reported using modified one-pot reaction conditions. In both cases yields were excellent and single diastereomers were obtained. FigureRapid preparation of 4-substituted glycosyl 1,2,3-triazole conjugates from glycosyl bromides.

Modified One‐Pot Protocol for the Preparation of Thioglycosides from Unprotected Aldoses via S‐Glycosyl Isothiouronium Salts*

An efficient one‐pot protocol for the direct preparation of thioglycosides starting from unprotected reducing sugars via S‐glycosyl isothiouronium salts is reported. In this one‐pot methodology, BF3 · OEt2 has been used as a general catalyst for both per‐O‐acetylation of sugars and conversion of sugar per‐O‐acetates into S‐glycosyl isothiouronium salts, which was allowed to react with alkylating agents in the presence of a base to furnish thioglycosides in excellent yield. *C.D.R.I. communication no. 6767. Authors contributed equally to this work.

Efficient acylation and sulfation of carbohydrates using sulfamic acid, a mild, eco-friendly catalyst under organic solvent-free conditions

A fast and efficient acylation of carbohydrate derivatives and free sugars using a stoichiometric quantity of acylating agents in the presence of sulfamic acid, an environmentally benign catalyst, under organic solvent-free conditions is reported. Excellent yields in the selective acylation and sulfation of carbohydrate derivatives have also been achieved using sulfamic acid as the catalyst. The reaction is fast and the yields were excellent.