The study looked at enzymes in legume plants that help them use nitrogen. They found that all legume species had a lot of one enzyme called glutamine synthetase in their nodules. Another enzyme, glutamate synthase, was found in varying amounts in different species. The levels of a third enzyme, glutamate dehydrogenase, also varied widely. The researchers discovered that most legume plants use a similar pathway to process ammonia in their nodules.