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Cytosolic and plastidic chorismate mutase isozymes from Arabidopsis thaliana : molecular characterization and enzymatic properties
Author(s) -
Eberhard Jenny,
Ehrler Thomas T.,
Epple Petra,
Felix Georg,
Raesecke HannsR.,
Amrhein Nikolaus,
Schmid Jürg
Publication year - 1996
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1996.10050815.x
Subject(s) - chorismate mutase , biochemistry , isozyme , aromatic amino acids , biology , tyrosine , amino acid , tryptophan , phenylalanine , cytosol , arabidopsis thaliana , shikimate pathway , tyrosine aminotransferase , enzyme , complementary dna , microbiology and biotechnology , gene , enzyme inducer , mutant
The three aromatic amino acids phenylalanine, tyrosine, and tryptophan are synthesized in the plastids of higher plants. There is, however, biochemical evidence that a cytosolic isoform exists of the enzyme catalysing the first step of that branch of the pathway which is specific for the synthesis of phenylalanine and tyrosine, i.e. chorismate mutase (CM). We now report on the isolation of a cDNA clone encoding a cytosolic CM isozyme from Arabidopsis thaliana that was identified by complementing a CM‐deficient Escherichia coli strain. The deduced amino acid sequence of this isozyme was 50% identical to that of a previously isolated plastidic CM, and 41% identical to that of yeast CM. The organ‐specific expression patterns of the two CM genes were rather similar, but only the gene encoding the plastidic isozyme was elicitor‐ and pathogen‐inducible. The plastidic CM expressed in E. coli was activated by tryptophan and inhibited by phenylalanine and tyrosine, whereas the cytosolic isozyme was insensitive. The existence of a cytosolic CM isozyme implies that either a cytosolic pathway (partial or complete) for the biosynthesis of phenylalanine and tyrosine exists, or that prephenate, originating from chorismate in the cytosol, is utilized for the synthesis of metabolites other than these two aromatic amino acids.