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An extreme-halophile archaebacterium possesses the interlock type of prephenate dehydratase characteristic of the Gram-positive eubacteriaThe focal point of phenylalanine biosynthesis is a dehydratase reaction which in different organisms may be prephenate dehydratase, arogenate dehydratase, or cyclohexadienyl dehydratase. Gram-positive, Gram-negative, and cyanobacterial divisions of the eubacterial kingdom exhibit different dehydratase patterns. A new extreme-halophile isolate, which grows on defined medium and is tentatively designated as Halobacterium vallismortis CH-1, possesses the interlock type of prephenate dehydratase present in Gram-positive bacteria. In addition to the conventional sensitivity to feedback inhibition by L-phenylalanine, the phenomenon of metabolic interlock was exemplified by the sensitivity of prephenate dehydratase to allosteric effects produced by extra-pathway (remote) effectors. Thus, L-tryptophan inhibited activity while L-tyrosine, L-methionine, L-leucine and L-isoleucine activated the enzyme. L-Isoleucine and L-phenylalanine were effective at micromolar levels; other effectors operated at mM levels. A regulatory mutant selected for resistance to growth inhibition caused by beta-2-thienylalanine possessed an altered prephenate dehydratase in which a phenomenon of disproportionately low activity at low enzyme concentration was abolished. Inhibition by L-tryptophan was also lost, and activation by allosteric activators was diminished. Not only was sensitivity to feedback inhibition by L-phenylalanine lost, but the mutant enzyme was now activated by this amino acid (a mutation type previously observed in Bacillus subtilis). It remains to be seen whether this type of prephenate dehydratase will prove to be characteristic of all archaebacteria or of some archaebacterial subgroup cluster.
Document ID
20040089494
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Jensen, R. A. (State University of New York at Binghamton 13901 United States)
d'Amato, T. A.
Hochstein, L. I.
Date Acquired
August 21, 2013
Publication Date
January 1, 1988
Publication Information
Publication: Archives of microbiology
Volume: 148
ISSN: 0302-8933
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: PCM-8316275
CONTRACT_GRANT: 33188-801
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Number 52-30
NASA Program Exobiology
NASA Center ARC
NASA Discipline Exobiology