The glucosinolate–myrosinase system. New insights into enzyme–substrate interactions by use of simplified inhibitors

Abstract

Myrosinase, a thioglucoside glucohydrolase, is the only enzyme able to hydrolyse glucosinolates, a unique family of molecules bearing an anomeric O-sulfated thiohydroximate function. Non-hydrolysable myrosinase inhibitors have been devised and studied for their biological interaction. Diverse modifications of the O-sulfate moiety did not result in a significant inhibitory effect, whereas replacing the D-glucopyrano residue by its carba-analogue allowed inhibition to take place. X-Ray experiments carried out after soaking allowed for the first time inclusion of a non-hydrolysable inhibitor inside the enzymatic pocket. Structural tuning of the aglycon part in its pocket is being used as a guide for the development of simplified and more potent inhibitors.

Crystal structure at 1.1Å resolution of an insect myrosinase from Brevicoryne brassicae shows its close relationship to β-glucosidases

“…These two fragments show two aspects of substrate binding to plant myrosinase, whereas directly prior to catalysis the substrate passes by some high-energy conformation, which cannot be observed directly. Still, the myrosinase aglycon binding site is relatively well-characterized, and results obtained for the S-ethyl inhibitor (Bourderioux et al, 2005) correspond to results obtained by modeling on other myrosinase-inhibitor complexes (Burmeister et al, 1997;Fig. 5.…”

“…A substrate analogue bound to the aglycon binding site could be observed, whereas the glucose group was bound in an obviously non-productive conformation (Bourderioux et al, 2005). It was possible to increase the aglycon binding by simplification of the glucose group to an ethyl group.…”

“…Figure made with Espript (Gouet et al, 1999). The aglycon binding site has been analyzed by a comparison with the myrosinase aglycon binding site ((Bourderioux et al, 2005), Fig. 5C).…”

Glucosinolate Chemistry: Synthesis of O‐Glycosylated Derivatives of Glucosinalbin

“…[28] O-Sulfation of the hydroximino moiety with the sulfur trioxide-pyridine complex followed by quenching with aqueous potassium hydrogen carbonate afforded the per-O-acetylated glucosinolates 27-31, which were readily deprotected under basic conditions to 1 and 32-35 (Scheme 4).…”

Detection oftrans–cisflips and peptide-plane flips in protein structures

“…12 of the 14 X-Xnpg tcÀ FN corresponded to cases for which a flip was observed or predicted in an NCS-related chain or in the MR search model [Asn267 in chain A and Glu435 in chain D of PDB entry 1fwx (Brown et al, 2000), Ser412 in PDB entries 1q7z and 1q85 (Evans et al, 2004), Ala458 in PDB entries 1w9b and 1w9d (Bourderioux et al, 2005) and Asp273 in PDB entries 3fx6 (Wang et al, 2009) and 3fvl (Wang et al, 2010)]. These FN will therefore in practice not be a large problem.…”