Researchers convert yeast into vital drug producing factories

Washington, Aug 16: Researchers have successfully converted yeast into a mini factory for churning out vital drugs, including anti-plaque toothpaste additives, antibiotics, nicotine, and even morphine.

Christina D. Smolke, assistant professor of chemical engineering at California Institute of Technology (Caltech), with graduate Kristy Hawkins, genetically modified common baker's yeast so that it contained the genes for several plant enzymes.

The enzymes allow yeast to produce a chemical called reticuline, a precursor for many different classes of benzylisoquinoline alkaloid (BIA) molecules.

The BIA molecules are a large group of chemically intricate compounds, such as morphine, nicotine, and codeine, which are naturally produced by plants.

BIA molecules exhibit a wide variety of pharmacological activities, including antispasmodic effects, pain relief, and hair growth acceleration. Other BIAs have shown anticancer, antioxidant, antimalarial, and anti-HIV potential.

"There are estimated to be thousands of members in the BIA family, and having a source for obtaining large quantities of specific BIA molecules is critical to gaining access to the diverse functional activities provided by these molecules," said Smolke.

Her lab focuses on using biology as a technology for the synthesis of new chemicals, materials, and products. However, the natural plant sources of BIAs accumulate only a small number of the molecules, usually "end products" like morphine and codeine that, while valuable, can't be turned into other compounds, thus limiting the availability of useful new products.

To their reticuline-producing yeast, Smolke and Hawkins added the genes for other enzymes, from both plants and humans, which allowed the yeast to efficiently generate large quantities of the precursors for sanguinarine, a toothpaste additive with antiplaque properties; berberine, an antibiotic; and morphine.

The researchers are now in the process of engineering their yeast so that they will turn these precursor molecules into the final, pharmacologically useful molecules.

These findings will be featured in the September issue of Nature Chemical Biology.