The genes for five subtilisin-libe serine proteases from alkaliphilic strains of Bacillus exhibiting resistance to oxidative inactivation were cloned and sequenced. The deduced amino acid sequences of the enzymes were highly homologous (greater than 88% identity). They were composed of 638 or 639 amino acids, including a possible similar to 200-amino acid prepro-peptide, and unique stretches of similar to 160 amino acids were found in the C-terminal regions. The molecular masses of mature enzymes (433 or 434 amino acids) were similar to 45 kDa for all. Amino acid sequence comparison and phylogenetic analysis indicated that these enzymes are far removed from other known subtilisins in the line of molecular evolution. We propose that these novel proteases be categorized as a new class of subtilisins, named oxidatively stable, alkaline protease.