No abstract

BackgroundThe glyoxylate cycle is thought to be present in bacteria, protists, plants, fungi, and nematodes, but not in other Metazoa. However, activity of the glyoxylate cycle enzymes, malate synthase (MS) and isocitrate lyase (ICL), in animal tissues has been reported. In order to clarify the status of the MS and ICL genes in animals and get an insight into their evolution, we undertook a comparative-genomic study.ResultsUsing sequence similarity searches, we identified MS genes in arthropods, echinoderms, and vertebrates, including platypus and opossum, but not in the numerous sequenced genomes of placental mammals. The regions of the placental mammals' genomes expected to code for malate synthase, as determined by comparison of the gene orders in vertebrate genomes, show clear similarity to the opossum MS sequence but contain stop codons, indicating that the MS gene became a pseudogene in placental mammals. By contrast, the ICL gene is undetectable in animals other than the nematodes that possess a bifunctional, fused ICL-MS gene. Examination of phylogenetic trees of MS and ICL suggests multiple horizontal gene transfer events that probably went in both directions between several bacterial and eukaryotic lineages. The strongest evidence was obtained for the acquisition of the bifunctional ICL-MS gene from an as yet unknown bacterial source with the corresponding operonic organization by the common ancestor of the nematodes.ConclusionThe distribution of the MS and ICL genes in animals suggests that either they encode alternative enzymes of the glyoxylate cycle that are not orthologous to the known MS and ICL or the animal MS acquired a new function that remains to be characterized. Regardless of the ultimate solution to this conundrum, the genes for the glyoxylate cycle enzymes present a remarkable variety of evolutionary events including unusual horizontal gene transfer from bacteria to animals.ReviewersArcady Mushegian (Stowers Institute for Medical Research), Andrey Osterman (Burnham Institute for Medical Research), Chris Ponting (Oxford University).

No abstract

No abstract

A new two-step process of production of succinic acid (SA) has been developed, which includes the microbial synthesis of alpha-ketoglutaric acid by the yeast Yarrowia lipolytica (step 1) and subsequent oxidation of the acid by hydrogen peroxide to SA (step 2). The maximum concentration of SA and its yield were found to be 63.4 g l(-1) and 58% of the ethanol consumed, respectively. The purity of the SA isolated from the culture liquid filtrate reached 100%. The yield of SA was as high as 82% of its amount in the culture liquid filtrate. The quality of the SA produced by the invented method meets the biochemical grade definitions, as is evident from the respiratory and other relevant parameters of rat liver mitochondria upon the oxidation of this SA.