But excess porphyrin is harmful. The scientists found a natural plant enzyme which deactivates porphyrins in plants and animals. The concept came from cooperative research between Dartmouth Medical School and ARS' Natural Products Utilization Research Unit in Oxford, Miss., on the campus of the University of Mississippi . In green plants, chlorophylls, which are derived from porphyrins, trap solar energy and turn it into food. Some herbicides prevent chlorophyll synthesis and cause porphyrins to accumulate to abnormally high levels.
Plants then become hypersensitive to light and die.
This works well for killing weeds, but since the herbicide is applied when crops are in the field they, too, could be injured. Crops could be bred, or genetically engineered, to enhance their levels of the enzyme that deactivates the porphyrins. This would protect the crops when the herbicide is applied. This discovery in plants may also lead to new ways of preventing or controlling porphyria, a human genetic disease. People affected with this condition also become hypersensitive to light.