The initial hypothesis that eukaryotes originate from symbiosis between bacteria and unknown host cells received support from phylogenetic analyses, leading to the proposition that mitochondria emerged from bacteria. According to this hypothesis, these bacteria would have been members of the Alphaproteobacteria class, but the identity of such members is not resolved yet. Although the metabolic pathways operative in the different Alphaproteobacteria are very diverse, some striking homologies are found when comparing amino acid metabolism in some Alphaproteobacteria and mitochondria. These homologies include the use of glutamate as energy substrate and as precursor of glutamine, the capacity to degrade proline, and to synthesize heme with the involvment of glycine. The cells that hosted Alphaproteobacteria are presumed to be members among the superphylum Asgard archaea, which share some characteristics with eukaryotic cells. Although Asgard archaea are metabolically versatile, some limited and recent data suggest possible metabolic interactions, and even metabolic cooperation, between archaea and Alphaproteobacteria in terms of amino acid metabolism. In fact, genome analysis suggests metabolic capacity of Asgard archaea for transport of amino acids in free form and as oligopeptides, and for biosynthesis of cysteine, methionine, glutamate, and serine.