Jan 1, 1976

Altered prephenate dehydratase in phenylalanine-excreting mutants of Brevibacterium flavum

Journal of Biochemistry
I Shiio, S Sugimoto


The regulatory properties of three key enzymes in the phenylalanine biosynthetic pathway, 3-deoxy-D-arabino-heptulosonate 7-phosphate synthetase (DAHP synthetase) [EC], chorismate mutase [EC], and prephenate dehydratase [prephenate hydro-lyase (decarboxylating), EC] were compared in three phenylalanine-excreting mutants and the wild strain of Brevibacterium flavum. Regulation of DAHP synthetase by phenylalanine and tyrosine in these mutants did not change at all, but the specific activities of the mutant cell extracts increased 1.3- to 2.8-fold, as reported previously (1). Chorismate mutase activities in both the wild and the mutant strains were cumulatively inhibited by phenylalanine and tyrosine and recovered with tryptophan, while the specific activities of the mutants increased 1.3- to 2.8-fold, like those of DAHP synthetase. On the other hand, the specific activities of prephenate dehydratase in the mutant and wild strains were similar, when tyrosine was present. While prephenate dehydratase of the wild strain was inhibited by phenylalanine, tryptophan, and several phenylalanine analogues, the mutant enzymes were not inhibited at all but were activated by these effectors. Tyrosine activated the m...Continue Reading

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Mentioned in this Paper

Enzymes, antithrombotic
2-Dehydro-3-Deoxyphosphoheptonate Aldolase
Phosphate Measurement
Prephenate Dehydratase
Enzymes for Treatment of Wounds and Ulcers

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