The discovery, by university researcher Peter Facchini and PhD student Scott Farrow, includes the first biochemical reaction of its kind ever reported in plants, which may also occur in garden-variety poppies and other plants.
Their research, published this week as a cover story in the Journal of Biological Chemistry
, sheds light on how the opium poppy - the world's only source of the valuable painkillers - evolved the ability to make morphine and other compounds.
"The functions of what we thought were really specific genes and enzymes involved in morphine biosynthesis are actually much broader," says Facchini, professor of biological sciences in the Faculty of Science and an internationally recognized expert on the opium poppy.
In 2010, Facchini's laboratory reported the discovery of two unique genes, and the enzymes they encode, that enable the opium poppy to synthesize morphine and codeine.
Enzymes are protein molecules - highly selective catalysts that accelerate both the rate and specificity of metabolic reactions.
The new finding shows that these enzymes in opium poppy, along with a third enzyme discovered by the U of C lab, "have these unexpected and widespread roles," Facchini says.
"There are more branches of related alkaloid metabolism that lead to a lot of different compounds that have different pharmacological and important biological properties in opium poppy."
The new insights could enable pharmaceutical companies to manipulate the biochemical pathway and create varieties of the opium poppy that produce higher levels of specific drugs, such as codeine or morphine, Facchini says.
Codeine is by far the most widely used opiate in the world and one of the most commonly used painkillers.
Codeine can be extracted directly from the opium poppy, although most of the painkiller is chemically synthesized from the much more abundant morphine found in the plant.
Canadians spend more than $100 million a year on codeine-containing pharmaceutical products and are among the world's top consumers of the drug per capita.
Facchini and Farrow suspect that the biochemical reactions they discovered also occur in garden-variety poppy species related to the opium poppy, as well as in other plants.
"The difference between related plants, in terms of their ability to make or not make morphine, might only be the activity of a single enzyme," Facchini notes.