Abstract:The cotton pathogen Xanthomonas campestris pv. malvacearum produces extracellular protease activity when grown in the presence of casein-proteins (skim-milk). At least three proteases are produced with apparent molecular weights of 29 kD, 38 kD and 43 kD. Protease-1 can be inhibited by phosphoramidone, EDTA and 1,10-phenanthroline and reactivated by incubating with zinc ions, suggesting that protease-1 is a metalloprotease. It was found that protease-1 only cleaved the peptide bond of aspartic acid and cysteic acid from N-terminal side, confirming previous observations. This property could be very useful for protein sequence analysis and preparation of specific peptides from larger proteins.