[Sialylation of N-carbohydrate chains of glycoproteins with immobilized trans-sialidase from Trypanosoma cruzi]. / Sialilirovanie N-uglevodnykh tsepei glikoproteinov s pomoshch'iu immobilizovannoi trans-sialidazy Trypanosoma cruzi.

Alpha2,3-sialylation of the lactosamine type N-glycans with trans-sialidase from Trypanosoma cruzi is reported. Trans-sialidase (160 kDa, pI 5.35-5.65) and its catalytic fragment (70 kDa, pI 6.0-6.3) were isolated from T. cruzi cells and immobilized on ConA-Sepharose. The resulting preparation retained activity for several months and was repeatedly used for obtaining mono-, di-, tri-, and tetrasialylated 7-amino-4-metylcoumarine-labeled oligosaccharides with various numbers of antennas and for alpha2,3-sialylation of glycans within glycoproteins and neoglycoconjugates.

New feature of angiotensin-converting enzyme: carbohydrate-recognizing domain.

Self carbohydrate-mediated dimerization of glycoprotein angiotensin-converting enzyme (ACE) was demonstrated. The dimerization was studied in the reverse micelle experimental system as a model of biomembrane situation. Asialo-ACE or agalacto-ACE was able to form a dimer, whereas deglycosylated ACE and sequentially desialylated and degalactosylated ACE failed to dimerize. ACE-ACE interaction was competitively inhibited by Neu5Ac- or Gal-terminated saccharides. The results have allowed us to propose the existence of carbohydrate-recognizing domain (CRD) on ACE molecule. The structural requirements of this CRD were estimated based on the ability of saccharides to inhibit ACE dimerization. The most effective monosaccharides with equal inhibition potencies were shown to be galactose (as GalbetaOMe) and N-acetylneuraminic acid (as Neu5AcalphaOMe). Among oligosaccharides, the most effective ones were found to be 3'SiaLac and, especially, the whole pool of ACE oligosaccharide chains and biantennae complex oligosaccharide chains of other glycoproteins. Bovine and human ACEs were shown to be similar in terms of recognition of carbohydrates.

Investigation of sialic acids and sialyltransferase activity in blood of patients with systemic scleroderma.

Systemic scleroderma (SSd) is a connective tissue disorder accompanied by generalized fibrosis. A disturbance of the synthesis and production of matrix glycoproteins, such as collagens, fibronectin, and proteoglycans, by connective tissue cells is typical for this disease. We previously demonstrated a decrease in the ganglioside content of cultured skin fibroblasts from patients with SSd. In this work the contents of sialoglycoproteins and sialoglycolipids in blood sera of patients with SSd were estimated. Simultaneously, the level of asialofetuin-sialyltransferase activity in blood plasma of three groups of patients--those with SSd, Raynaud's phenomenon, and with localized scleroderma--was investigated. CMP-5-acetamido-9-deoxy-9-fluoresceinylthioureidoneuraminic acid was used as a substrate for the enzyme assay. It was shown that the concentration of total sialic acid was increased and the concentration of lipid-bound sialic acid was slightly decreased in the blood sera of patients with SSd. A correlation between the lipid-bound sialic acid level and the severity of disease was observed; there was no correlation between severity of disease and total sialic acid. Sialyltransferase assay showed a decrease in the activity level in all three groups of patients. The greatest decrease (2-fold) of this activity was observed in patients with Raynaud's phenomenon. Our data suggest that in SSd and similar diseases the process of glycoconjugate sialylation is disturbed. These changes may considerably affect the mechanisms of regulation of metabolism and cellular interactions.

[Structure of carbohydrate chains of molecular forms of alpha1-acidic glycoprotein from ascitic fluid from patients with stomach cancer]. / Struktura uglevodnykh tsepei molekuliarnykh form alpha1-kislogo glikoproteina iz astsitnoi zhidkosti bol'nykh rakom zheludka.

The immunochemically pure alpha 1-acid glycoprotein (aAGP) from ascitic fluid of patients with stomach cancer was separated by chromatography on Con A-Sepharose into Con A-nonbound (aAGP-1, 43, 5 kDa, 70%) and Con A-bound (aAGP-2, 41.5 kDa, 24% and aAGP-3, 40.0 kDa, 5%) forms, differing in the monosaccharide composition. Comparative study of structures of their N-carbohydrate chains with the aid of the HPLC of fluorescence-labelled oligosaccharides showed that the molecular forms differ by the ratio of the di-, tri-, and tetraantennary carbohydrate N-chains of a complex type. The molecular forms of aAGP differ from nAGP by amounts of Le(x)-fragments and agalacto-oligosaccharides.

[Conjugates and carbohydrate chains of alpha 1-acid glycoprotein with polyacrylamide maintain the immunomodulating activity of native glycoprotein]. / Kon''iugaty uglevodnykh tsepei alpha1-kislogo glikoproteina s poliakrilamidom sokhraniuiut immunomoduliruiushchuiu aktivnost' prirodnogo glikoproteina.

Translocation of carbohydrate glycoprotein N-chains onto soluble polyacrylamide was proposed as a method for studying the biological role of carbohydrate chains. N-linked carbohydrate chains of alpha 1-acid glycoprotein (AGP) were aminated at the reducing GlcNAc moiety and covalently attached to polyacrylamide (PAA). Thus "pseudo-AGP" was obtained where peptide core was replaced with PAA. The synthetic model mimics AGP by M(r) and carbohydrate content as well as the ratio of tetra-, tri- and diantennary and mono-, di-, tri- and tetrasialo chains. It was shown that the conjugate inhibits proliferation of lymphocytes like the parent AGP. Therefore, the property of AGP to inhibit the lymphocyte proliferation is attributed to its carbohydrate chains, whereas peptide core serves as carrier providing polyvalent interaction of multiple carbohydrate chains with cell.

Albumin-like glycoprotein from human fetal tissue.

Albumin-like glycoprotein (Gp66) with a molecular mass of 66 kDa has been isolated from human fetal tissue by size-exclusion, ion-exchange chromatography and reverse-phase HPLC. Reactivity of Gp66 with antiserum raised against the major protein components fraction of human fetal serum was observed. The N-terminal 35 amino acid residues of Gp66 were identical to human serum albumin. Meanwhile Gp66 differed from albumin by a/ the presence of 3-5 Trp residues instead of 1 according to fluorescence and UV-spectra, b/ the glycosylation pattern: bi-, tri-, and tetraantennary sialooligosaccharides of a complex type were present. Isoelectric focusing revealed 4 isoforms (pI ranging within 4.8 to 5.1) of Gp66. Gp66 (but not asialo-Gp66) was able to inhibit the cytotoxic effect of TNF against the tumor cell line L929. Inhibition of WEHI-3 and L929 tumor cells proliferation by Gp66 was similar to that of albumin.

[Molecular forms of alpha-1-acid glycoprotein in human blood serum. Differences in levels of di-, tri-, and tetra-antennary N-linked carbohydrate chains]. / Molekuliarnye formy alpha-1-kislogo glikoproteina syvorotki krovi cheloveka. Razlichiia v soderzhanii di-, tri-, i tetraantennykh N-uglevodnykh tsepei.

alpha 1-Acid glycoprotein isolated from healthy individuals blood was separated on Con A-Sepharose into three fractions: non-bound (AGP-1, 84%, 43.5 kDa), Con A-bound (AGP-2, 14%, 41.3 kDa), and Con A-tightly bound (AGP-3, 2%, 39.6 kDa). Amino acid compositions of these fractions were similar but carbohydrate ones differed. HPLC analysis of 7-amino-4-methylcoumarin derivatives of the oligosaccharides in combination with their sequential exoglycosidase digestion showed that AGP-1, AGP-2, and AGP-3 have the same set of oligosaccharides and differ only by their proposition. A minor quantity of agalacto-oligosaccharides (with a terminal GlcNAc residue) was identified.

[Fluorescent derivatives of carbohydrates in the analysis of the structure of glycoconjugates. N-(4-methylcoumarin-7-yl) glycamines in the study of asparagine-bound carbohydrate chains of glycoproteins]. / Fluorestsentnye proizvodnye uglevodov v strukturnom analize glikokon''iugatov. N-(4-metilkumarin-7-il)glikaminy v izuchenii asparaginsviazannykh uglevodnykh tsepei glikoproteinov.

4-(N-Methylcoumarin-7-yl) glycamines were employed in studying asparagine-linked carbohydrate chains of acid desialylated fetuin. The procedure was optimised for the reductive amination of oligosaccharides with 7-amino-4-methylcoumarin in the presence of Na(CN)BH3 to lead to oligosaccharide glycamines (AMC-OS). AMC-OS were obtained from dextran oligosaccharides and from oligosaccharides released by hydrazinolysis of asparagine-linked sugar chains of asialofetuin. Reverse-phase HPLC and exclusion HPLC with fluorimetric quantitation of AMC-OS is described. TSK Gel 2000 SW column was calibrated using dextran AMC-OS to give linear relationship ln Ni = k(ti/tr)+b, where ti/tr is retention time of the AMC-OS relatively to the reference AMC-trisaccharide, and Ni is calibration unit value, characterizing molecular size of AMC-OS. Three AMC-OS, Gal3GlcNAc3Man3GlcNAc2-AMC (I) and (II), and Gal2GlcNAc3Man3GlcNAc2AMC (III), were obtained from asialofetuin in a molar ration of 1:1.8:0.1. Acid treatment of AMK-OS (II) in desialylation conditions also gave AMC-OS (III), thus suggesting a partial degalactosylation of the glycoprotein sugar chains during the desialylation. Consequent digestion of AMC-OS (II) and (III) with Jack bean beta-galactosidase and beta-N-acetylhexosaminidase led to the same AMC-OS, Man3GlcNAc2AMC. The final digestion product of AMC-OS (I) was GalGlcNAcMan3GlcNAc2AMC, suggesting a structural difference in one of the antennas of the minor sugar chain of asialofetuin. The monosaccharide quantitation and exoglycosidase sequencing were carried out at a 100 pmole level.