Cloning and characterization of the ddc homolog encoding L-2,4-diaminobutyrate decarbosylase in Enterobacter aerogenes

L-2,4-Diaminobutyrate decarboxylase (DABA DC) catalyzes the formation of 1, 3-diaminopropane (DAP) from DABA. In the present study, the ddc gene encodi ng DABA DC from Enterobacter aerogenes ATCC 13038 was cloned and characteri zed, Determination of the nucleotide sequence revealed an open reading fram e of 1470 bp encoding a 53659-Da protein of 490 amino acids, whose deduced NH2-terminal sequence was identical to that of purified DABA DC from E. aer ogenes. The deduced amino acid sequence was highly similar to those of Acin etobacter baumannii and Haemophilus influenzae DABA DCs encoded by the ddc genes. The lysine-307 of the E. aerogenes DABA DC was identified as the pyr idoxal 5'-phosphate binding residue by site-directed mutagenesis, Furthermo re, PCR analysis revealed the distribution of E. aerogenes ddc homologs in some other species of Enterobacteiacene. Such a relatively wide occurrence of the ddc homologs implies biological significance of DABA DC and its prod uct DAP.