Enzymes from insect-eating plants could give us new antibacterial products.

Carnivorous plants are not the first organisms to come to mind when searching for biomedical compounds. Yet, like something from science fiction, researchers are discovering enzymes in the digestive fluids of carnivorous pitcher plants that could prove useful in controlling infections.

Most plants support their growth by absorbing nutrients such as nitrogen, phosphorus and potassium from the soil. But for those unlucky enough to live in regions where soils lack these nutrients, alternative arrangements have evolved — such as organs that can catch, kill and digest insects.

Some of these organs develop as spiky mouths that close on unsuspecting insects when they land on them; some develop as seemingly normal leaves that are covered with goo, rather like flypaper; others, such as the structures sported by the plant Nepenthes alata, are slippery pitchers that function like pit traps. Nepenthes alata uses a combination of bright colours and sweet scent to attract insects to the pitcher, where slippery side walls and a deep pit filled with acidic fluid trap and kill the victims.

The fluid at the base of the trap had long been thought to contain digestive enzymes. Previous research had confirmed this, but exactly which enzymes were present was anyone’s guess. “Digestion in pitcher plants has been actively studied for more than 150 years and we still don’t know how it works [because] it is such a complex process,” says Chris Frazier at the University of New Mexico in Albuquerque.

Now, Naoya Hatano from the Harima Institute in Riken and Tatsuro Hamada from Ishikawa Prefectural University in Japan have identified seven proteins in the carnivorous plant's fluid. They grew the carnivorous plants in their lab, and collected the fluid from newly opened pitchers to prevent contamination from recently captured insects. Then they used polyacrylamide gel electrophoresis to separate out the proteins, and mass spectrometry to identify what type of enzymes the proteins were likely to be. Because some of the enzymes they found were unfamiliar, they searched protein databases to find enzymes with similar structures and noted that some of them were probably not digestive at all.

http://www.nature.com/news/2008/080131/full/news.2008.546%20.html