CONICET | Buscador de Institutos y Recursos Humanos

Phosphotransacetylases (PTA) catalyzes the reversible interconversion of acetyl-CoA and acetyl phosphate. Distinct isoforms of PTA are expressed in prokaryotic organisms, where they play diverse metabolic roles. Surveys of sequenced microbial genomes reveal two classes of Pta enzymes. Class I enzymes (PtaI) are ~350 residues in length, whereas class II enzymes (PtaII) are twice as long as PtaI (~700 residues). PtaI enzymes share end-to-end homology with the C-terminal domain of PtaII enzymes. Two PTA genes have been identified by sequence homology in Escherichia coli : pta and eutD. Pta belongs to the PtaII class and it is codified within the ack-pta operon1 whereas eutD belongs to the PtaI class and it is codified within the 17-gene ethanolamine utilization operon2. The aim of the present work was the biochemical characterization of Pta and EutD in order to make a comparison between both enzymes. With this purpose, the proteins were purified and kinetically characterized. The product of both enzymes displays PTA activity, although EutD is a more efficient phosphotransacetylase than Pta in catalyzing its reaction in either direction and assembles as a dimer, being differentially modulated than Pta by several effectors. The growth on acetate of the E. coli pta acs double-mutant strain, was complemented by either introducing EutD or by Pta. Overall, the results indicate that EutD and Pta, although able to catalyse the same reaction, display differential efficiency and regulation, and also differ in the induction of their expression. However, under certain growth conditions, they can fulfil equal roles in E. coli metabolism. References:1. Wolfe A.J., Microbiol Mol Biol Rev, 69, 1250 (2005)2. Kofoid, E., Rappleye C., Stojiljkovic I., and Roth J., J. Bacteriol, 181, 5317-5329 (1999)