The oxidative stability of alpha-amylase (AmyC) from Thermotoga maritima was improved by mutating the methionine residues at positions 43 and 44, 55, and 62 to oxidative-resistant alanine residues. The most resistant M55A variant showed 50% residual activity in the presence of 100 mM H2O2, whereas the wild-type enzyme was inactive. (C) 2013, The Society for Biotechnology, Japan. All rights reserved.