title: Peanut (Arachis hypogaea) lectin recognizes alpha-linked galactose, but not N-acetyl lactosamine in N-linked oligosaccharide terminals.
abstract: Peanut (Arachis hypogaea) agglutinin (PNA) is extensively used as tumour marker as it strongly recognises the cancer specific T antigen (Galbeta1-->3GalNAc-), but not its sialylated version. However, an additional specificity towards Galbeta1-->4GlcNAc (LacNAc), which is not tumour specific, had been attributed to PNA. For correct interpretation of lectin histochemical results we examined PNA sugar specificity using naturally occurring or semi-synthetic glycoproteins, matrix-immobilised galactosides and lectin-binding tissue glycoproteins, rather than mono- or disaccharides as ligands. Dot-blots, transfer blots or polystyrene plate coatings of the soluble glycoconjugates were probed with horse-radish peroxidase (HRP) conjugates of PNA and other lectins of known specificity. Modifications of PNA-binding glycoproteins, including selective removal of O-linked oligosaccharides and treatment with glycosidases revealed that Galbeta1-->4GlcNAc (LacNAc) was ineffective while terminal alpha-linked galactose (TAG) as well as exposed T antigen (Galbeta1-->3 GalNAc-) was excellent as sugar moiety in glycoproteins for their recognition by PNA. When immobilised, melibiose was superior to lactose in PNA binding. Results were confirmed using TAG-specific human serum anti-alpha-galactoside antibody.
authors.affiliation: Biochemistry Division, Sree Chitra Tirunal Institute for Medical Sciences and Technology, 695011, Thiruvananthapuram, India.
authors.forename: B K
authors.initials: BK
authors.lastname: Chacko
authors.forename: P S
authors.initials: PS
authors.lastname: Appukuttan
mesh_terms: D000606:Amino Sugars / Q000737:chemistry*; D000915:Antibody Affinity; D000957:Antigens, Viral, Tumor / Q000737:chemistry; D002352:Carrier Proteins / Q000737:chemistry; D005690:Galactose / Q000737:chemistry*; D006023:Glycoproteins / Q000737:chemistry*; D006735:Horseradish Peroxidase; D037102:Lectins / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry*; D010084:Oxidation-Reduction; D019887:Peanut Agglutinin / Q000737:chemistry*; D037121:Plant Lectins
chemical_list: D000606:Amino Sugars; D000957:Antigens, Viral, Tumor; D002352:Carrier Proteins; D006023:Glycoproteins; D037102:Lectins; D009844:Oligosaccharides; D019887:Peanut Agglutinin; D037121:Plant Lectins; C043696:jacalin; C000458:N-acetyllactosamine; D006735:Horseradish Peroxidase; D005690:Galactose