Clues from a halophilic methanogen about aromatic amino acid biosynthesis in archaebacteria

摘要: Extensive diversity in features of aromatic amino acid biosynthesis and regulation has become recognized eubacteria, but almost nothing is known about the extent to which such exists within archaebacteria. Methanohalophilus mahii, a methylotrophic halophilic methanogen, was found synthesize l-phenylalanine l-tyrosine via phenylpyruvate 4-hydroxyphenylpyruvate, respectively. Enzymes capable using l-arogenate as substrate were not found. Prephenate dehydrogenase highly sensitive feedback inhibition by could utilize either NADP+ (preferred) or NAD+ cosubstrate. Tyrosine-pathway dehydrogenases having combination narrow specificity for cyclohexadienyl broad pyridine nucleotide cofactor have been described before. The chorismate mutase enzyme member class insensitive allosteric control. most noteworthy character state prephenate dehydratase proved be subject multimetabolite control inhibitor (l-phenylalanine) activators (l-tyrosine, l-tryptophan, l-leucine, l-methionine l-isoleucine). This interlock type dehydratase, also broadly distributed among gram-positive lineage previously shown exist extreme halophile, Halobacterium vallismortis. results are consistent with conclusion based upon 16S rRNA analyses that Methanomicrobiales halophiles cluster together.