Comparison of the nucleotide sequences of the meta-cleavage pathway genes of TOL plasmid pWW0 from Pseudomonas putida with other meta-cleavage genes suggests that both single and multiple nucleotide substitutions contribute to enzyme evolution.

摘要: TOL plasmid pWW0 from Pseudomonas putida mt-2 encodes catabolic enzymes required for the oxidation of toluene and xylenes. The structural genes these are clustered into two operons, xylCMABN operon, which a set transformation toluene/xylenes to benzoate/toluates, xylXYZLTEGFJQKIH benzoate/toluates Krebs cycle intermediates. latter operon can be divided physically functionally parts, xylXYZL cluster, is involved in (methyl)catechols, xylTEGFJQKIH (methyl)catechols Genes isofunctional present Acinetobacter calcoaceticus, constitute benzoate-degradative pathway, while homologous encoding methylphenol-degradative pathway naphthalene-degradative on pVI150 P. CF600, NAH7 PpG7, respectively. Comparison nucleotide sequences with other suggested that diverged homologues 20 50 million years ago, A. calcoaceticus 100 200 ago. In codons where amino acids not conserved, substitution rate third base was higher than synonymous codons. This result interpreted as indicating both single multiple substitutions contributed acid-substituting mutations, hence enzyme evolution. observation seems general because mammalian globin exhibit same tendency.