Evolution of mammalian X-linked and autosomal Pgk and Pdh E1 alpha subunit genes

The phylogeny and substitution rates of the mammalian X chromosome- locatedand autosomal phosphoglycerate kinase and pyruvate dehydrogenase genes wereinvestigated. Compatibility analysis was used to show reticulate evolutionin these genes. Analysis of the marsupial, mouse, and humanphosphoglycerate kinase genes suggests that at least two recombinationevents have taken place, one occurring about the time of theplacental-marsupial split involving exons 1-5 and the other before theprimate-rodent split involving exons 9-10. Similar analysis of the pyruvatedehydrogenase genes indicates a recombination event involving exons 2-3 ata time before the primate-rodent split and a gene conversion between exons3-4 in the human somatic and testis- specific pyruvate dehydrogenase genesafter the primate-rodent split. This demonstrates that genetic exchange canoccur between paralogous genes at widely separated chromosomal locations.Estimation of nucleotide substitution rates in these genes confirmed ahigher substitution rate in the pyruvate dehydrogenase genes. In thephosphoglycerate kinase genes, there is no difference between thesubstitution rates in mice and humans and between the X chromosome- andautosome-located genes. A greater substitution rate was noted in the mouseautosomal pyruvate dehydrogenase gene when compared with the other mouseand human genes. This may be a result of either directional naturalselection or a relaxation of functional constraint at this specific gene.