Summary: The and genes encoding the acetate-activating enzymes acetate kinase and phosphotransacetylase were isolated, subcloned on a plasmid and re-introduced into Relative to the wild-type, the recombinant strains showed about tenfold higher specific activities of both enzymes. Sequence analysis of a 3657 bp DNA fragment revealed that the and genes are contiguous in the corynebacterial chromosome, with upstream and the last nucleotide of the stop codon (TAA) overlapping the first of the start codon (ATG). The predicted gene product of consists of 329 amino acids ( 35242), that of consists of 397 amino acids ( 43098) and the amino acid sequences of the two polypeptides show up to 60% (phosphotransacetylase) and 53% (acetate kinase) identity in comparison with respective enzymes from other organisms. Northern (RNA) blot hybridizations using and -specific probes and transcriptional fusion experiments revealed that the two genes are transcribed as a 2·5 kb bicistronic mRNA and that the expression of this operon is induced when grows on acetate instead of glucose as a carbon source. Directed inactivation of the chromosomal and genes led to the absence of detectable phosphotransacetylase and acetate kinase activity in the respective mutants and to their inability to grow on acetate. These data indicate that no isoenzymes of acetate kinase and phosphotransacetylase are present in and that a functional acetate kinase/phosphotransacetylase pathway is essential for growth of this organism on acetate.


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