Comparative Regulation of Isoenzymic 3-Deoxy-d-arabino-Heptulosonate 7-Phosphate Synthetases in Microorganisms

摘要: The independent control of regulatory isoenzymes by different metabolites constitutes one well-known pattern in branched metabolic pathways. This was previously found to be widely distributed the aromatic amino acid pathway microorganisms case first enzyme sequence, 3-deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthetase. comparative stability as well effect acids growth medium upon levels individual were shown for Salmonella typhimurium. Several lines evidence are discussed demonstrate strong reliance Escherichia coli phenylalanine-sensitive isoenzyme ordinary biosynthetic needs wild-type strains. frequent occurrence “dominant” species which resist repressive effects inhibitory end products noted. lack an obligatory correlation level activity and synthesis product specifically controls its is used discount possibility that each might feed a unique separate pool end-product precursor. An isoenzymic DAHP synthetase sensitive feedback inhibition low tryptophan fractionated from tyrosine- cell-free extracts Neurospora crassa.