Synthesis and biological evaluation of novel biotin–iminoalditol conjugates

The effect of a covalent and a noncovalent small-molecule inhibitor on the structure of Abg β-glucosidase in the gas-phase

The effects of binding two small-molecule inhibitors to Agrobacterium sp. strain ATCC 21400 (Abg) β-glucosidase on the conformations and stability of gas-phase ions of Abg have been investigated. Biotin-iminosugar conjugate (BIC) binds noncovalently to Abg while 2,4-dinitro-2-deoxy-2-fluoro-β-D-glucopyranoside (2FG-DNP) binds covalently with loss of DNP. In solution, Abg is a dimer. Mass spectra show predominantly dimer ions, provided care is taken to avoid dissociation of dimers in solution and dimer ions in the ion sampling interface. When excess inhibitor, either covalent or noncovalent, is added to solutions of Abg, mass spectra show peaks almost entirely from 2:2 inhibitor-enzyme dimer complexes. Tandem mass spectrometry experiments show similar dissociation channels for the apo-enzyme and 2FG-enzyme dimers. The +21 dimer produces +10 and +11 monomers. The internal energy required to dissociate the +21 2FG-enzyme to its monomers (767 ± 30 eV) is about 36 eV higher than that for the apo-enzyme dimer (731 ± 6 eV), reflecting the stabilization of the free enzyme dimer by the 2FG inhibitor. The primary dissociation channels for the noncovalent BIC-enzyme dimer are loss of neutral and charged BIC. The internal energy required to induce loss of BIC is 482 ± 8 eV, considerably less than that required to dissociate the dimers. For a given charge state, ions of the covalent and noncovalent complexes have about 15 % and 25 % lower cross sections, respectively, compared with the apo-enzyme. Thus, binding the inhibitors causes the gas-phase protein to adopt more compact conformations. Noncovalent binding surprisingly produces the greatest change in protein ion conformation, despite the weaker inhibitor binding. ᅟ

Imino sugars and glycosyl hydrolases: historical context, current aspects, emerging trends

Forty years of discoveries and research on imino sugars, which are carbohydrate analogues having a basic nitrogen atom instead of oxygen in the sugar ring and, acting as potent glycosidase inhibitors, have made considerable impact on our contemporary understanding of glycosidases. Imino sugars have helped to elucidate the catalytic machinery of glycosidases and have refined our methods and concepts of utilizing them. A number of new aspects have emerged for employing imino sugars as pharmaceutical compounds, based on their profound effects on metabolic activities in which glycosidases are involved. From the digestion of starch to the fight against viral infections, from research into malignant diseases to potential improvements in hereditary storage disorders, glycosidase action and inhibition are essential issues. This account aims at combining general developments with a focus on some niches where imino sugars have become useful tools for glycochemistry and glycobiology.