Biochemical Journal

Research article

Long-lived glycosyl-enzyme intermediate mimic produced by formate re-activation of a mutant endoglucanase lacking its catalytic nucleophile

Josep-Lluís VILADOT, Francesc CANALS, Xavier BATLLORI, Antoni PLANAS

Abstract

The mutant E134A 1,3-1,4-β-glucanase from Bacillus licheniformis, in which the catalytic nucleophilic residue has been removed by mutation to alanine, has its hydrolytic activity rescued by exogenous formate in a concentration-dependent manner. A long-lived α-glycosyl formate is detected and identified by 1H-NMR and matrix-assisted laser desorption ionization–time-of-flight-MS. The intermediate is kinetically competent, since it is, at least partially, enzymically hydrolysed, and able to act as a glycosyl donor in transglycosylation reactions. This transient compound represents a true covalent glycosyl-enzyme intermediate mimic of the proposed covalent intermediate in the reaction mechanism of retaining glycosidases.

  • chemical rescue
  • covalent intermediate
  • glycosidase mechanism
  • glycosynthase
  • 1,3-1,4-β-glucanase