title: Evidence for pentagalloyl glucose binding to human salivary alpha-amylase through aromatic amino acid residues.
abstract: We demonstrate here that pentagalloyl glucose (PGG), a main component of gallotannins, was an effective inhibitor of HSA and it exerted similar inhibitory potency to Aleppo tannin used in this study. The inhibition of HSA by PGG was found to be non-competitive and inhibitory constants of K(EI)=2.6 microM and K(ESI)=3.9 microM were determined from Lineweaver-Burk secondary plots. PGG as a model compound for gallotannins was selected to study the inhibitory mechanism and to characterize the interaction of HSA with this type of molecules. Surface plasmon resonance (SPR) binding experiments confirmed the direct interaction of HSA and PGG, and it also established similar binding of Aleppo tannin to HSA. Saturation transfer difference (STD) experiment by NMR clearly demonstrated the aromatic rings of PGG may be involved in the interaction suggesting a possible stacking with the aromatic side chains of HSA. The role of aromatic amino acids of HSA in PGG binding was reinforced by kinetic studies with the W58L and Y151M mutants of HSA: the replacement of the active site aromatic amino acids with aliphatic ones decreased the PGG inhibition dramatically, which justified the importance of these residues in the interaction.
authors.affiliation: Department of Biochemistry, University of Debrecen, H-4010 Debrecen P.O. Box 55, Hungary. gyemant@puma.unideb.hu
authors.forename: Gyöngyi
authors.initials: G
authors.lastname: Gyémánt
authors.forename: Agnes
authors.initials: A
authors.lastname: Zajácz
authors.forename: Bálint
authors.initials: B
authors.lastname: Bécsi
authors.forename: Chandran
authors.initials: C
authors.lastname: Ragunath
authors.forename: Narayanan
authors.initials: N
authors.lastname: Ramasubbu
authors.forename: Ferenc
authors.initials: F
authors.lastname: Erdodi
authors.forename: Gyula
authors.initials: G
authors.lastname: Batta
authors.forename: Lili
authors.initials: L
authors.lastname: Kandra
mesh_terms: D024322:Amino Acids, Aromatic / Q000378:metabolism*; D020134:Catalytic Domain; D005960:Glucosides / Q000378:metabolism; D006801:Humans; D047348:Hydrolyzable Tannins / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D055291:Salivary alpha-Amylases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D013634:Tannins / Q000378:metabolism
chemical_list: D024322:Amino Acids, Aromatic; D005960:Glucosides; D047348:Hydrolyzable Tannins; D013634:Tannins; C519396:aleppo tannin; C435084:pentagalloylglucose; D055291:Salivary alpha-Amylases