title: Enzyme inhibition by iminosugars: analysis and insight into the glycosidase-iminosugar dependency of pH.
abstract: Imino- and azasugar glycosidase inhibitors display pH dependant inhibition reflecting that both the inhibitor and the enzyme active site have groups that change protonation state with pH. With the enzyme having two acidic groups and the inhibitor one basic group, enzyme-inhibitor complexes with three (EH3I), two (EH2I), one (EHI), or no protons (EI), are possible. In the present work an analysis method is presented that from pH-inhibition data allows one to distinguish between the different complexes and determine which protonation state is preferred. It is also possible to determine the pH-independent binding constants of the inhibitor. Analysis of pH data for imino- and azasugar inhibition of β-glucosidases revealed that basic glycosidase inhibitors bind as the monoprotonated (EHI) complex. Three neutral inhibitors were also studied and two of these were also bound exclusively as the EHI complex while a third bound both as a EHI and a EH2I complex.
authors.affiliation: Department of Organic Chemistry, University of Seville, Profesor García González 1, 41012 Seville, Spain.
authors.forename: Óscar
authors.initials: Ó
authors.lastname: López
authors.forename: Feng-Ling
authors.initials: FL
authors.lastname: Qing
authors.forename: Christian Marcus
authors.initials: CM
authors.lastname: Pedersen
authors.forename: Mikael
authors.initials: M
authors.lastname: Bols
mesh_terms: D001372:Aza Compounds / Q000737:chemistry; D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D050111:Imino Sugars / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D011485:Protein Binding; D011522:Protons
chemical_list: D001372:Aza Compounds; D004791:Enzyme Inhibitors; D050111:Imino Sugars; D011522:Protons; D006026:Glycoside Hydrolases
keywords: Azasugar; Enzyme; Inhibition; pH; pK(a)