Leucine biosynthesis in the blue-green bacterium Anacystis nidulans.

AUTOR(ES)
RESUMO

Leucine-requiring auxotrophs of the unicellular blue-green bacterium Anacystis nidulans have been isolated. Extracts of these mutants were deficient in alpha-isopropylmalate synthetase (EC 4.1.3.12). In wild-type cells, this enzyme was subject to feedback inhibition by leucine. However, formation of the enzymes of leucine biosynthesis was little affected by exogenous leucine in either wild-type or mutant strains. Cultures of the latter subjected to extreme leucine deprivation showed no change in specific activity of beta-isopropylmalate isomerase (EC 4.2.1.33) and at most a 50% increase in the specific activity of beta-isopropylmalate dehydrogenase (EC 1.1.1.85). These results are compared with others bearing on the evolution of the control of amino acid biosynthesis in blue-green bacteria.

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