OCCURRENCE OF A NOVEL L-2,4-DIAMINOBUTYRATE DECARBOXYLASE ACTIVITY INSOME SPECIES OF ENTEROBACTERIACEAE, AND PURIFICATION AND CHARACTERIZATION OF THE ENZYMES OF ENTEROBACTER-AEROGENES AND SERRATIA-MARCESCENS

L-2,4-Diaminobutyrate decarboxylase (DABA DC) is a novel enzyme yieldi ng 1,3-diaminopropane (DAP) from DABA, which has previously been purif ied from strains of the genera Vibrio and Acinetobacter. In this study , we also detected DABA DC activity in the species of Enterobacteriace ae: E. aerogenes, E. cloacae, E. agglomerans, Serratia marcescens, S. liquefaciens, Klebsiella pneumoniace, K. oxytoca and Citrobacter freun dii, all of which produced DAP in sufficient amounts. Subsequently, th e DABA DCs of E. aerogenes and S. marcescens were purified to homogene ity and characterized. Two separate enzymes had similar properties wit h respect to chromatographic behaviors, and were a dimer with subunits of identical molecular mass of about 51 kDa. The maximal activity of each enzyme was obtained at pH 8.0-8.25. Both enzymes required pyridox al 5'-phosphate and Mg2+ for full activity, and were highly specific f or L-DABA. There was immunological similarity, but not identity betwee n these proteins, as determined by Ouchterlony double diffusion analys is with antiserum against the E. aerogenes DABA DC. They showed the sa me N-terminal amino acid sequence up to the 8th residue (S-K-L-N-P-I-L -A-). These enzymes were different in molecular mass, N-terminal amino acid sequence and antigenicity from DABA DCs of Acientobacter and Vib rio species.