In contrast to their counterparts in bacteria and animals the soluble inorganic pyrophosphatases from plant cells are active as monomers. The isoforms 1 and 4 from <em>Arabidopsis thaliana</em> have been characterized with more detail, but their three-dimensional structure is unavailable. Here, a recently published protocol (ROSETTA design-HMMer), is used to guide well-known techniques for homology-modeling, in the production of reliable models for the three-dimensional structure of these two arabidopsis isoforms. Their interaction with magnesium ions and pyrophosphate is analyzed <em>in silico</em>in silico.