Regulation der Biosynthese der aromatischen Aminosäuren in Claviceps paspali

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Abstract
DAHP‐synthetase, chorismate mutase, prephenate dehydrogenase, prephenate dehydratase and anthranilate synthease were identified in extracts of Claviceps paspali mycelium. We were able to separate three DAHP‐synthetases, one sensitive to l‐phenylalanine, one sensitive to l‐tyrosine and one sensitive to l‐tryptophan. The l‐tryptophan sensitive isoenzyme provided the main part of the DAHP‐synthetase activity (about 60%). The inhibition due to l‐tryptophan was not removed by l‐tyrosine nor l‐phenylalanine. Chorismic acid did not inhibit these enzymes. Chorismate mutase was inhibited by l‐tyrosine and also by l‐phenylalanine, though these inhibitions were only detected after purification of the enzyme, and even then the highly purified enzyme (ca. 100‐fold) could not be separated into isoenzymes. The inhibition of the purified enzyme by l‐tyrosine and l‐phenylalanine could be removed entirely by l‐tryptophan.Prephenate dehydratease was inhibited only by l‐phenylalanine and it could not be activated by l‐tyrosine nor l‐tryptophan.Prephenate dehydrogenase showed an inhibiting effect by l‐tyrosin only after purification.Anthranilate synthetase was not inhibited by l‐tryptophan even after purification.Anthranilate synthetase was not inhibited by l‐tryptophan even after purification. With the simultaneous additions of l‐tyrosine, l‐phenylalanine and l‐tryptophan (in equal concentrations of 1 × 10−3 M) no repression effects could be produced.