Protein Painkiller

Injecting mice with the natural protein prostatic acid phosphatase (PAP) suppresses pain as effectively as morphine but for much longer, according to an international research team led by Mark J. Zylka of the University of North Carolina, Chapel Hill, and Pirkko Vihko of the University of Helsinki, in Finland (Neuron 2008, 60, 111). The researchers report that one dose of PAP works for up to three days, whereas a dose of morphine lasts just five hours. Scientists have studied PAP for 70 years, but they have remained unsure about its function and thought it was produced only in the prostate gland. Zylka, Vihko, and colleagues now have found that one form of PAP is identical to fluoride-resistant acid phosphatase, a previously discovered protein that is produced by pain-sensing neurons. When stimulated, these neurons release adenosine triphosphate (ATP), which activates pathways that create the sensation of pain. The pain fades as ATP loses phosphate groups and degrades to adenosine. The researchers showed that PAP aids this degradation by removing the phosphate group from adenosine monophosphate. Zylka says PAP could "be a groundbreaking treatment for pain."