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B6db references: 3069843

type Journal Article
authors Inoue, K.; Kuramitsu, S.; Aki, K.; Watanabe, Y.; Takagi, T.; Nishigai, M.; Ikai, A.; Kagamiyama, H.
title Branched-chain amino acid aminotransferase of Escherichia coli: overproduction and properties
journal J Biochem (Tokyo)
Activity 2.6.1.42
Family 2.6.1.42
sel selected
ui 3069843
year (1988)
volume 104
number 5
pages 777-84
 
keywords Amino Acid Sequence
abstract ilvE gene of Escherichia coli was inserted into the region downstream of the tac promotor. As a result, the branched-chain amino acid aminotransferase was overproduced by about a hundred-fold in E. coli W3110. The overproduced aminotransferase was purified from cell extracts about 40-fold to homogeneity. Chemical and physicochemical analyses confirmed that it was a product of the ilvE gene. The enzyme existed in a hexamer with a subunit molecular weight of 34,000; the double trimer model of the enzyme presumed by the previous chemical cross-linking experiments (Lee-Peng, F.-C. et al. (1979) J. bacteriol. 139, 339-345) was supported by electron micrographs. The circular dichroic (CD) spectrum of branch-chain amino acid aminotransferase had double negative maxima at 210 and 220 nm. The alpha-helical content was estimated to be about 40% from the CD spectrum in the region of 200 to 250 nm. The absorption spectrum of the enzyme showed two peaks at 330 and 410 nm. There was no pH-dependent spectral shift. The CD spectrum of the coenzyme, pyridoxal 5'-phosphate, had negative peaks at 330 and 410 nm. These spectral properties of branched-chain amino acid aminotransferase were quite different from those of E. coli aspartate aminotransferase. Each subunit bound approximately 1 mol of pyridoxal 5'-phosphate. A lysyl residue, which forms a Schiff base with the aldehyde group of the pyridoxal 5'-phosphate, was identified in the primary structure of the enzyme.
last changed 2009/05/04 17:50

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