Abstract: A novel protease is described. The enzyme has the following characteristics: molecular weight: 30,000 (a gel filtration method using Sephadex G-75); isoelectric point, 5.3; pH reactivity: the optimum pH for its esterase activity is at pH 8.5 and the optimum pH for its amidase activity is at pH 9.0 respectively; substrate reactivity: it selectively and specifically hydrolyzes the ester bond and the amide bond derived from the carboxyl group of L-lysine; inhibitor: it is inhibited by diisopropyl phosphofluoride, tosyl-L-lysine chloro-methyl ketone and phenylmethylsulfonyl chloride. The protease is preferably produced by a microorganism belonging to the genus Achromobacter.

Abstract: A process for preparing B30-threonine-insulin which comprising reacting a des-B30-insulin with an excess amount of threonine derivative in the presence of an enzyme specifically acting on a lysine carbonyl in peptide bondings and produced by Achromobacter lyticus M 497-1.

Abstract: A process for preparing a B30-threonine-insulin which comprising reacting a des-B30-insulin with an excess amount of threonine derivative in the presence of an enzyme specifically acting on a lysine carbonyl in peptide bondings and produced by Achromobacter lyticus M 497-1.