Publications

• 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.

  Ikai H., Yamamoto S.

  The ca. 2.2-kbp region upstream of the ddc gene encoding L-2,4-diaminobutyrate decarboxylase in Acinetobacter baumannii was sequenced and found to contain another open reading frame of 1,338 nucleotides encoding a protein with a deduced molecular mass of 47,423 Da. Analysis of the homologies obser ... >> More

  The ca. 2.2-kbp region upstream of the ddc gene encoding L-2,4-diaminobutyrate decarboxylase in Acinetobacter baumannii was sequenced and found to contain another open reading frame of 1,338 nucleotides encoding a protein with a deduced molecular mass of 47,423 Da. Analysis of the homologies observed from the deduced amino acid sequence indicated that the gene product is an enzyme belonging to subgroup II of the aminotransferases. This was first verified when examination of the crude extracts from Escherichia coli transformants led to detection of a novel aminotransferase activity catalyzing the following reversible reactions: L-2,4-diaminobutyric acid + 2-ketoglutaric acid<-->L-glutamic acid + L-aspartic beta-semialdehyde. Further confirmation was obtained when 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 the nucleotide sequence. Therefore, the gene and its product were named dat and L-2,4-diaminobutyrate:2-ketoglutarate 4-aminotransferase (DABA AT), respectively. Feeding experiments of A. baumannii with L-[U-14C]aspartic acid resulted in the incorporation of the label into 1,3-diaminopropane. Apparent homologs of dat and DABA AT were detected in other Acinetobacter species by PCR amplification and Western blotting. These results indicate that the dat gene (as well as the ddc gene) participates in the synthesis of 1,3-diaminopropane, the only diamine found in this genus. However, the biological role, if one exists, of 1,3-diaminopropane synthesis is unknown. << Less

  J. Bacteriol. 179:5118-5125(1997) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Two genes involved in the 1,3-diaminopropane production pathway in Haemophilus influenzae.

  Ikai H., Yamamoto S.

  We previously cloned and sequenced the Acinetobacter baumannii dat and ddc genes encoding L-2,4-diaminobutyrate: 2-ketoglutarate 4-aminotransferase (DABA AT) and DABA decarboxylase, respectively, involved in the 1,3-diaminopropane (DAP) production pathway. Homology searches of the gene products pr ... >> More

  We previously cloned and sequenced the Acinetobacter baumannii dat and ddc genes encoding L-2,4-diaminobutyrate: 2-ketoglutarate 4-aminotransferase (DABA AT) and DABA decarboxylase, respectively, involved in the 1,3-diaminopropane (DAP) production pathway. Homology searches of the gene products provided an indication that a similar gene cluster is present in the genome of Haemophilus influenzae Rd. This was first verified by detection of the corresponding enzyme activities in and the production of DAP by all H. influenzae strains examined. Both of the crude enzymes from the representative strain of H. influenzae showed catalytic properties essentially similar to the A. baumannii DABA AT and DABA DC. An Escherichia coli clone carrying the dat homolog of H. influenzae Rd showed a high level of DABA AT activity, the enzyme protein responsible being detected by immunoblot analysis. These results specify the two H. influenzae genes involved in DAP production. << Less

  Biol. Pharm. Bull. 21:170-173(1998) [PubMed] [EuropePMC]

• Characterization of biosynthetic enzymes for ectoine as a compatible solute in a moderately halophilic eubacterium, Halomonas elongata.

  Ono H., Sawada K., Khunajakr N., Tao T., Yamamoto M., Hiramoto M., Shinmyo A., Takano M., Murooka Y.

  1,4,5,6-Tetrahydro-2-methyl-4-pyrimidinecarboxylic acid (ectoine) is an excellent osmoprotectant. The biosynthetic pathway of ectoine from aspartic beta-semialdehyde (ASA), in Halomonas elongata, was elucidated by purification and characterization of each enzyme involved. 2,4-Diaminobutyrate (DABA ... >> More

  1,4,5,6-Tetrahydro-2-methyl-4-pyrimidinecarboxylic acid (ectoine) is an excellent osmoprotectant. The biosynthetic pathway of ectoine from aspartic beta-semialdehyde (ASA), in Halomonas elongata, was elucidated by purification and characterization of each enzyme involved. 2,4-Diaminobutyrate (DABA) aminotransferase catalyzed reversively the first step of the pathway, conversion of ASA to DABA by transamination with L-glutamate. This enzyme required pyridoxal 5'-phosphate and potassium ions for its activity and stability. The gel filtration estimated an apparent molecular mass of 260 kDa, whereas molecular mass measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was 44 kDa. This enzyme exhibited an optimum pH of 8.6 and an optimum temperature of 25 degreesC and had Kms of 9.1 mM for L-glutamate and 4.5 mM for DL-ASA. DABA acetyltransferase catalyzed acetylation of DABA to gamma-N-acetyl-alpha,gamma-diaminobutyric acid (ADABA) with acetyl coenzyme A and exhibited an optimum pH of 8.2 and an optimum temperature of 20 degreesC in the presence of 0.4 M NaCl. The molecular mass was 45 kDa by gel filtration. Ectoine synthase catalyzed circularization of ADABA to ectoine and exhibited an optimum pH of 8.5 to 9.0 and an optimum temperature of 15 degreesC in the presence of 0.5 M NaCl. This enzyme had an apparent molecular mass of 19 kDa by SDS-PAGE and a Km of 8.4 mM in the presence of 0. 77 M NaCl. DABA acetyltransferase and ectoine synthase were stabilized in the presence of NaCl (>2 M) and DABA (100 mM) at temperatures below 30 degreesC. << Less

  J. Bacteriol. 181:91-99(1999) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.