Canadian researchers have discovered the genes responsible for crucial steps in the manufacture of morphine by poppies, raising the possibility of plants that produce medically-useful codine but cannot be used for heroin.

Jillian Hagel and Peter Facchini, of the University of Calgary, report in Nature Chemical Biology that they have identified the enzymes responsible for two of the three chemical steps that convert the amino acid tyrosine to morphine. They also identified the genes that produce these enzymes.

“The enzymes encoded by these two genes have eluded plant biochemists for a half-century,” says Facchini (press release). “In finding not only the enzymes but also the genes, we’ve made a major step forward. It’s equivalent in finding a gene involved in cancer or other genetic disorders.”

Shutting down the production of morphine at the right point could mean that plants produced only codine – a widely used painkiller – and not morphine, which is used to make heroin. As Facchini and Hagel note in their paper, cultivation of the opium poppy (Papaver somniferum L.) is the sole commercial source for codine and derivatives such as oxycodone.

A poppy which could produce codine but not heroin would be useful in places like Afghanistan, where production for illicit use is prevalent and attempts to encourage cultivation for medical purposes are often stymied by concerns about heroin production (see: Opiates for the masses).

Image: Facchini with poppies / Ken Bendiktsen, University of Calgary