PURIFICATION AND CHARACTERIZATION OF DIPEPTIDYL AMINOPEPTIDASE FROM AUREOBACTERIUM SP WO26

We isolated a bacterial strain with an enzyme which releases dipeptide from Gly-Arg-p-nitroanilide. The bacterium was tentatively identified as Aureobacterium sp. The enzyme, named AuDAP, was purified and chara cterized, It was homogenous by SDS-PAGE and IEF, and had a molecular m ass of 90,000 Da by SDS-PAGE and 88,000 Da by gel filtration, so it ma y be a monomer, The isoelectric point was 3.8 and the optimum pH was 1 0.0, The purified enzyme hydrolyzed Gly-Arg-pNA, a model substrate for DAP I, and Arg-Arg-MNA, a model substrate for DAP III, However, this enzyme did not hydrolyze Gly-Phe pNA, also a model substrate for DAP I , These results suggested that this enzyme did not fall under the clas sification of mammalian DAPs and was similar to DAP BI from Pseudomona s sp, WO24 and dDAP from Dictyostelium discoideum, although several di fferences were observed between them, The N-terminal amino acid sequen ce of this enzyme showed no significant homology to any enzyme and pro tein, except only for DAP BI.