NOVELTY - Modified Bacillus subtilisin (I) where at least one amino acid residue, such as amino acid residues 62, 217, 222, 156 or 166, is replaced by cysteine residues, where the cysteine residues are modified by replacing the thiol hydrogen with a substituent group providing a thiol side chain, is new.    USE - (I) is useful for detergent formulations, in bar or liquid soap applications, dish care formulations, contact lens cleaning solutions or products, peptide synthesis, feed applications such as feed additives or preparation of feed additives, waste treatment, textile applications such as treatment of fabrics, to treat silk or wool, as fusion-cleavage enzymes in protein production and in organic synthesis for e.g. to catalyze a desired reaction and/or favor a certain stereoselectivity.    ADVANTAGE - The modified enzymes have increased activity, altered pH profiles, improved wash performance, nucleophile specificity, substrate specificity, stereoselectivity, thermal stability and surface binding properties as compared to the native enzymes. The modified enzymes can be used in cleaning composition without detergents when used in animal feed for cereal-based feeds. They also enable the crude protein value and/or digestibility and/or amino acid content and/or digestibility coefficients of the feed to be increased, which permits a reduction in the amounts of alternative protein sources and/or amino acids supplements which had previously been necessary ingredients of animal feeds.    DETAILED DESCRIPTION - Modified Bacillus subtilisin (I) comprises at least one amino acid residue, such as amino acid residues 62, 217, 222, 156 or 166, being replaced by cysteine residues, where the cysteine residues are modified by replacing the thiol hydrogen with a substituent group providing a thiol side chain. This is achieved by replacing the thiol hydrogen with a substituent group providing a thiol side chain chosen from -SR1R2, -SR3, -SR4 and -SR5, where:    (i) R1 is an alkyl moiety;    (ii) R2 is charged or polar moiety;    (iii) R3 is substituted or unsubstituted phenyl;    (iv) R4 is substituted or unsubstituted cyclohexyl; or    (v) R5 is 10-15C alkyl.    INDEPENDENT CLAIMS are also included for the following:    (1) producing (I);    (2) a detergent additive comprising (I);    (3) a feed additive comprising (I); and    (4) a composition for treating a textile comprising (I).