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The enzyme for a low-cholesterol diet.

The enzyme for a low-cholesterol diet

By converting one double bond into a single bond, the enzyme cholesterol reductase changes cholesterol into coprostanol. And that change can be important, because unlike cholesterol, coprostanol is not absorbed by the human body. Researchers at Iowa State University in Ames are attempting to isolate and harness cholesterol reductase to lower the cholesterol content of milk, eggs, meats and butter.

Their work initially focused on Eubacteria, microbes that contain cholesterol reductase and inhabit the large intestine. They added Eubacteria to high-cholesterol foods and incubated them at the microbes' normal temperature -- about 98.6[deg.]F. While this reduced the foods' cholesterol content 80 percent, it also caused the foods to spoil--an effect due at least in part to the temperature. That's one reason the Iowa researchers want to extract the enzyme and add it to foods directly.

Their most recent work suggests the microbes' conversion of cholesterol involves a three-step process--and possibly the activity of three genes. This suggests that identifying the operant genes and splicing them into other microbes--so that the enzyme could be commercially produced -- might prove difficult, says Donald Beitz, a nutritional biochemist leading the work.

So now he's focusing on plants. Though cholesterol is made only by animals, Beitz and his co-workers recently found the enzyme that converts it to coprostanol in the leaves of cucumbers, corn, soybeans and peas. Moreover, their preliminary data suggest coprostanol synthesis by the plant's enzyme, may be a one-step process--involving one gene--and one gene might prove easier to splice into E. coli or other bacteria that might be used for commercially mass-producing the enzyme. Beitz envisions the day when the shells of eggs coming down a conveyor belt might be drilled open, injected with the enzyme (and perhaps with a pretreating enzyme) and resealed. By the time an egg is eaten, he says, it cholesterol might be all but gone.
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Publication:Science News
Date:Jul 23, 1988
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