New aspects of the molecular evolution of legumains, Asn-specific cysteine proteinases.

The molecular evolution of asparagine-specific cysteine proteinases, called legumains, from plants and animals was analyzed using newly available related amino acid sequences from lower eukaryotes, bacteria and Archaea. The results suggest that genuine legumains originate from prokaryote pro-legumains. The evolutionary roots of genuine legumains from plants and animals descend from Parabasalia and Alveolata before developing into their respective separate branches headed by Chlorophyta and Placozoa. The branch of legumain-like plant/animal glycosylphosphatidyl inositol transamidases separated from the general evolutionary stem of legumains at the level of lower eukaryotes. Modeling of the 3D structure of a plant genuine legumain underlined the previously suggested similarity of the active site geometry of legumains with caspases, which are Asp-specific bacterial and eukaryote proteinases.