Glyphosate Metabolism

The article "End of an Era" renewed my concerns about the molecular metabolic pathways of glyphosate (C&EN, July 20, page 30). I looked these up after seeing the similarity with methyl glycine or sarcosine in two separate articles in the Feb. 16 issue. Sarcosine was reported as a significant biomarker in human urine for prostate cancer and was shown in vitro to induce invasive growth in healthy prostate tissue (page 8). When I flipped the pages to the article on "Greening the Farm," I was stunned to see the glyphosate structure looking so similar to sarcosine (page 13). The article indicated that Greenpeace rather liked glyphosate because it has relatively low toxicity—how ironic if there are other problems.

A quick search shows that indeed common soil organisms metabolize glyphosate readily to sarcosine, although it is not the main metabolite. I have to wonder about the source of the elevated sarcosine in human urine. Is glyphosate residue in our diets and environmental exposure altering enzyme activities because its mode of action is enzyme inhibition for amino acid synthesis? Has our exposure increased since the introduction of glyphosate-tolerant genetically modified crops? Has anyone else speculated on this potential interaction now that the sarcosine biomarker is being studied?

We are playing with fire, hosing massive quantities of powerful chemicals into the environment and our food chain. Unintended consequences are commanding teachers.

John Rudesill
Columbia, Md.