RRC ID 29720
著者 Gelfand DH, Steinberg RA.
タイトル Escherichia coli mutants deficient in the aspartate and aromatic amino acid aminotransferases.
ジャーナル J Bacteriol
Abstract Two new mutations are described which, together, eliminate essentially all the aminotransferase activity required for de novo biosynthesis of tyrosine, phenylalanine, and aspartic acid in a K-12 strain of Escherichia coli. One mutation, designated tyrB, lies at about 80 min on the E. coli map and inactivates the "tyrosine-repressible" tyrosine/phenylalanine aminotransferase. The second mutation, aspC, maps at about 20 min and inactivates a nonrespressible aspartate aminotransferase that also has activity on the aromatic amino acids. In ilvE- strains, which lack the branched-chain amino acid aminotransferase, the presence of either the tyrosine-repressible aminotransferase or the aspartate aminotransferase is sufficient for growth in the absence of exogenous tyrosine, phenylalanine, or aspartate; the tyrosine-repressible enzyme is also active in leucine biosynthesis. The ilvE gene product alone can reverse a phenylalanine requirement. Biochemical studies on extracts of strains carrying combinations of these aminotransferase mutations confirm the existence of two distinct enzymes with overlapping specificities for the alpha-keto acid analogues of tyrosine, phenylalanine, and aspartate. These enzymes can be distinguished by electrophoretic mobilities, by kinetic parameters using various substrates, and by a difference in tyrosine repressibility. In extracts of an ilvE- tyrB- aspC- triple mutant, no aminotransferase activity for the alpha-keto acids of tyrosine, phenylalanine, or aspartate could be detected.
巻・号 130(1)
ページ 429-40
公開日 1977-4-1
DOI 10.1128/jb.130.1.429-440.1977
PMID 15983
PMC PMC235221
MeSH Aspartate Aminotransferases / metabolism* Aspartic Acid / biosynthesis Chromosome Mapping Chromosomes, Bacterial Coliphages Escherichia coli / enzymology* Genes* Leucine / biosynthesis Mutation Phenylalanine / biosynthesis Transaminases / metabolism* Transduction, Genetic Tyrosine / biosynthesis Tyrosine Transaminase / metabolism*
IF 3.006
リソース情報
原核生物(大腸菌) ME8601 ME8600 ME8602