Molecular dynamics simulations have been performed on the lipase B from Candida antarctica (CalB) in its native form and with one or two oxidized residues, either methionine oxidized to methionine sulphoxide, tryptophan oxidized to 5- hydroxytryptophan, or cystine oxidized to a pair of cysteic acid residues. The results indicate that the methionine and tryptophan oxidations led to rather restricted changes in the structure, whereas the oxidation of cystines, which also caused cleavage of the cystine S–S linkage, gave rise to larger changes in the protein structure. Only two oxidized residues caused significant changes in the structure of the active site, viz. those of the Cys-64/22 and Cys-258/216 pairs. Site-directed mutagenesis of four mutants (M83I, M129L, W155Q and M72S) was also studied by molecular dynamics. The results from simulations give some clues to the direction of further work on stabilization.
