A galactomannan-hydrolysing α-galactosidase from jack fruit (Artocarpus integrifolia) seed: Affinity chromatographic purification and properties.

An acid α-galactosidase from the seeds of the jack fruit seed (Artocarpus integrifolia) has been purified to homogeneity by affinity chromatography on a matrix formed by cross-linking the soluble α-galactose-bearing guar seed galactomannan. The 35kDa enzyme was a homotetramer of 9·5kDa subunits. Its carbohydrate part (5·5%) was composed of galactose and arabinose. The Km with p-nitrophenyl α-D-galactoside as substrate was 0·35 mM. The Ki values indicated inhibition by galactose, 1-O-methyl α-galactose and melibiose in the decreasing order. Among α-galactosides, the enzyme liberated galactose from melibiose, but not from raffinose or stachyose at its pH optimum (5·2). The guar seed galactomannan was however efficiently degalactosidated; limited enzyme treatment abolished the precipitability of the polysaccharide by the α-galactose-specific jack fruit seed lectin, and complete hydrolysis yielded insoluble polysaccharide. Though similar in sugar specificity and subunit assembly, α-galactosidase and the lectin coexisting in the jack fruit seed gave no indication of immunological identity.

Physicochemical properties and binding-site amino acid residues of galactoside-binding protein of human placenta.

The galactose-binding lectin of human placenta has been purified to homogeneity by affinity chromatography on asialo-fetuin column. The protein, extractable from the tissue only with lactose is apparently membrane-bound. Molecular weight determination of native protein and subunit indicated a dimer of 13·4 kDa subunits. Inhibition of haemagglutination with various saccharides indicate that thiodigalactoside is the best inhibitor followed by lactose· However, p-nitrophenyl- and 1-O-methyl derivatives of galactose showed that α-anomers inhibited slightly better than β-anomer. Modification of amino acid residues indicated involvement of arginine, lysine and histidine residues at the saccharidebinding site. Cysteine residue modificatioin also abolished haemagglutinating activity. Amino acid composition of the lectin is also presented·

Oligosaccharide structure determination of glycoconjugates using lectins.

Lectins, the divalent or polyvalent (glyco) proteins of non-immune origin of the cells agglutinate cells or other materials, that display more than one saccharide of sufficient complementarity. Lectins considered 'identical' in terms of mono- and disaccharide specificity can be differentiated by their ability to recognise the fine differences in more complex structures. The present review discusses the interaction of lectins with various oligosaccharides and their resultant separations due to structural variations.

Binding site amino acid residues of jack fruit (Artocarpusintegrifolia) seed lectin: Chemical modification and protein difference spectral studies.

The effect of chemical modification of amino acid residues essential for sugar binding in the α-D-galactoside specific jack fruit (Artocarpus integrifolia) seed lectin and the protection of the residues by specific sugar from modification were studied. Citraconylation or maleylation of 75 % of its lysyl residues or acetylation of 70 % of the tyrosyl residues completely abolished sugar binding and agglutination without dissociation of subunits. 1-Omethyl α-D-galactoside could protect its essential lysyl and tyrosyl groups from modification. Tryptophan could not be detected in the protein. Difference absorption spectra on binding of the above sugar confirmed the role of tyrosine residues and showed an association constant Κ = 0·4 × 103 Μ-1. Data suggests that the lectin could be immobilized without any loss of sugar binding activity.

Plant lectins specific for N-acetyl-β-D-galactosamine.

N-Acetyl-D-galactosamine in β-linkage being ubiquitous in cell surface glycoproteins, their interaction with lectins specific for this sugar moiety may be a significant event in cell adhesion phenomena. This article discusses the common β-N-acetyl galactosamine-specific lectins, with particular stress on the lectin from winged beans (Psophocarpus tetragonolobus).

α -D-Galactose-specific lectin from jack fruit (A rtocarpus integra) seed.

An α-D-galactose-specific lectin from the seeds of jack fruit (Artocarpus integra) has been isolated in pure form by affinity chromatography on immobilised guar gum (a galactomannan). The lectin is shown to be a glycoprotein containing 3% carbohydrate and having a molecular weight of 39,500 as determined by gel filtration. Sodium dodecyl sulphate gel electrophoresis revealed a single polypeptide of 10,500 dalton, indicating that the native lectin is a tetrarner of identical subunits. The hemagglutinating activity of the lectin towards erythrocytes of all blood groups is found to be the same.

Isolation and characterization of lysosomal alpha-mannosidase of placental tissue.

The acidic α-mannosidase was purified 4400-fold by affinity chromatography on Concavalin A-Sepharose and heat treatment at 65°C in the presence of 1 mM zinc ion. The enzyme did not resolve into multiple forms as in the case of enzymes from human liver and human kidney. The pH optimum of the enzyme was 4.2 in citrate-phosphate buffer. The Km value for p-nitrophenyl-α-D-mannose was 1.9 mM. The molecular weight of the enzyme determined by gel filtration was 300,000. The enzyme contained 10.6% neutral sugars.