News article: Fruit Juices can inhibit cell enzymes

Following on from the biochemical individuality post, this was announced yesterday at the 236th National Meeting of the American Chemical Society by David G. Bailey, Ph.D. of the University of Western Ontario in London, Ontario; the researcher who first discovered grapefruit greatly inhibits CYP3A4 activity, in 1989. In this case he is saying a few fruit juices can affect 2 enzymes; one that helps with absorption from the small intestine (meaning the drug wouldn't be absorbed as much as expected), and the other (CYP3A4) which clears the drug from the blood once it has been absorbed (meaning it will take far longer than expected to clear from the bloodstream). The main point is that he feels many things will affect these enzymes. In the diet, often the strongest inducers/inhibitors would be things like herbs, spices, fruit and vegetables. It is normal for things to induce/inhibit most of the detox enzymes, often favorably, but if there is a shortage/vulnerability/overload of any detox enzyme, it is more likely to have a bad effect.

Note: The CYP450 enzyme mentioned relates only to intestinal CYP3A4. It is not currently thought to affect hepatic CYP3A4, which is where CYP3A4 is mostly situated.

http://www.sciencedaily.com/releases/2008/08/080819160050.htm

...By contrast, drugs whose levels are boosted in the presence of grapefruit juice appear to block an important drug metabolizing enzyme, called CYP3A4, that normally breaks down drugs.

"This is just the tip of the iceberg," Bailey says. "I'm sure we'll find more and more drugs that are affected this way."

To date, grapefruit, orange and apple juices have been shown to lower the absorption of etoposide, an anticancer agent; certain beta blockers (atenolol, celiprolol, talinolol) used to treat high blood pressure and prevent heart attacks; cyclosporine, a drug taken to prevent rejection of transplanted organs; and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole). But additional drugs are likely to be added to the list as physicians become more aware of this drug-lowering interaction, Bailey says...

examples:
http://www.ncbi.nlm.nih.gov/pubmed/11489435
http://www.ncbi.nlm.nih.gov/pubmed/14641551
http://www.greenjournal.org/cgi/content/full/105/2/429
http://www.globalrph.com/gfruit.htm

keywords/concepts
inhibition/induction
substrate
CYP3A4 (The 'busiest' of the CYP450 family of enzymes)
intestinal CYP3A4, hepatic CYP3A4