IDENTIFICATION AND ANALYSIS OF A GENE ENCODING L-2,4-DIAMINOBUTYRATE-2-KETOGLUTARATE 4-AMINOTRANSFERASE INVOLVED IN THE 1,3-DIAMINOPROPANE PRODUCTION PATHWAY IN ACINETOBACTER-BAUMANNII
H. Ikai et S. Yamamoto, IDENTIFICATION AND ANALYSIS OF A GENE ENCODING L-2,4-DIAMINOBUTYRATE-2-KETOGLUTARATE 4-AMINOTRANSFERASE INVOLVED IN THE 1,3-DIAMINOPROPANE PRODUCTION PATHWAY IN ACINETOBACTER-BAUMANNII, Journal of bacteriology, 179(16), 1997, pp. 5118-5125
The ca. 2.2-kbp region upstream of the ddc gene encoding L-2,4-diamino
butyrate decarboxylase in Acinetobacter baumannii was sequenced and fo
und to contain another open reading frame of 1,338 nucleotides encodin
g a protein with a deduced molecular mass of 47.323 Da. Analysis of th
e homologies observed from the deduced amino acid sequence indicated t
hat the gene product is an enzyme belonging to subgroup II of the amin
otransferases. This was first verified when examination of the crude e
xtracts from Escherichia coli transformants led to detection of a nove
l aminotransferase activity catalyzing the following reversible reacti
ons: L-2,4-diaminobutyric acid + 7-ketoglutaric acid<->L-glutamic acid
+ L-aspartic beta-semialdehyde. Further confirmation was obtained whe
n the gene was overexpressed in E. coli and the corresponding protein
was purified to homogeneity. It catalyzed the same reactions and its N
-terminal amino acid sequence was consistent with that deduced from th
e nucleotide sequence, Therefore, the gene and its product were named
dar and L-2,4-diaminobutyrate:2-ketoglutarate 4-aminotransferase (DABA
AT), respectively, Feeding experiments of A. baumannii with L-[U-C-14
]aspartic acid resulted in the incorporation of the label into 1,3-dia
minopropane Apparent homologs of dat and DABA AT were detected in othe
r Acinetobacter species by PCR amplification and Western blotting, The
se results indicate that the dat gene (as well as the dde gene) partic
ipates in the synthesis of 1,3-diaminopropane, the only diamine found
in this genus. However, the biological role, if one exists, of 1.3-dia
minopropane synthesis is unknown.