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When chemistry professor John Dawson makes small talk about his research at cocktail parties, people often sit up and take notice.
It’s not that he’s investigating a cure for cancer or even the common cold, but the object of his research—a class of enzymes called cytochrome P450—plays an intriguing role in human metabolism.
“Cytochrome P450 enzymes metabolize caffeine, so if you’re one of those people who can drink coffee in the evening and still fall asleep, you’ve probably got a high level of those enzymes,” Dawson said.
Along with caffeine, cytochrome P450 also metabolizes other medications, preventing them from building up to toxic levels in the body. The enzymes also synthesize new compounds such as estrogen and testosterone. But P450’s effects aren’t always beneficial.
“It is known that P450 can metabolize certain compounds into DNA-altering substances, which, of course, can lead to cancer,” Dawson said, “so its ability to break down insoluble materials can be good and bad. I’ve referred to this in journal articles as the Jekyll and Hyde effect of P450.”
Because of the complexity of these enzymes—there are at least 50 different types of cytochrome P450 in humans and hundreds more in plants—Dawson’s research has focused on their fundamental functions and structure. His work during the past 26 years at USC has provided a foundation for cancer researchers and pharmaceutical companies who target the enzyme in their studies.
Dawson’s more than 150 research publications and $5.3 million in research funding also have earned recognition from the Memphis Section of the American Chemical Society, which honored him with the 2003 Southern Chemist Award. Recently, he was named the 2004 Carolina Trustee Professor.
“My wife jokes that I’ve been studying the same thing for more than 30 years and that it might be time to move on to something else,” Dawson said. “But there’s a lot that we still don’t know about cytochrome P450.”
For example, pharmaceutical companies have discovered that the cytochrome P450 in grapefruit juice can inhibit the metabolism of certain cholesterol reducing drugs. Individuals who are prescribed Lipitor, for example, are warned not to drink grapefruit juice after taking the drug. To do so would thwart their own cytochrome P450’s ability to eventually metabolize the drug.
“It’s quite possible that there are other interactions with these enzymes that could have similar effects,” Dawson said.
Over the years, several of his 26 Ph.D. graduates have gone to work for pharmaceutical manufacturers who are eager to use their expertise in cytochrome P450. Dawson, who is editor of the Journal of Inorganic Biochemistry and will chair the 2005 Gordon Research Conference on Metals in Biology, currently has five graduate students in his lab together with his long-time colleague, Research Professor Masanori Sono. Over 50 undergraduates have worked in his lab during his tenure at USC.
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