By Sean Henahan, Access Excellence

The peroxidase enzyme is a key component of diagnostic kits used to evaluate numerous viral, bacterial and parasitic diseases, including AIDS and malaria. Purdue University geneticist Rick Vierling, director of the Genetics Laboratory for the Indiana Crop Improvement Association, started experimenting with soybean peroxidase because it is a hot "green" industrial commodity that can be extracted from soybean seed coats. Vierling says researchers have found ways to extract peroxidase from the soybean hulls without reducing the value of the oil or the meal in the beans.

The soy enzyme replaces horseradish peroxidase, which is an integral part of current diagnostic kits. Standard kits lose effectiveness in about four months without refrigeration, while preliminary research suggests that kits made with soybean peroxidase should last unrefrigerated for at least a year. This improvement would be especially important in places where refrigeration is problematic such as China, Africa and Central America.

The discovery is important from the environmental standpoint because peroxidase replaces harsh chemicals that might otherwise be used in the tests. Manufacturers are interested in soybean peroxidase because the supply of horseradish peroxidase is limited and the horseradish enzyme isn't very stable at high temperatures.

"All plants contain peroxidase, but not all peroxidase is created equal," Vierling says. "Soybean peroxidase is highly reactive and thermally stable. I don't think there's a better peroxidase out there."

As Vierling measured enzyme levels in beans, he saw that a quick, chemical test for peroxidase activity would greatly speed his research and plant breeding efforts. He developed one -- and in doing so, he noted that his technique was similar to medical diagnostic test kits that use horseradish peroxidase. He suspected that the medical kits might work better if they were made with the soy peroxidase. His preliminary tests confirmed his suspicions.

Vierling sent samples of soybean peroxidase to John Morrow, a professor at Texas Tech University's Health Science Center in Lubbock, Texas. Morrow and Vierling had worked together when Vierling was a graduate student. Vierling asked Morrow to substitute soybean peroxidase for horseradish peroxidase in clinical diagnostic tests.

"I was lukewarm about the idea at first," says Morrow, "but when I tried it, I was converted. I think he's got something that's a nice improvement over current technology."

The new development will be presented at the annual meeting of the American Association of Clinical Chemistry in Atlanta, July 22-23, 1997.