Biochemical consequences of phosphorylcholines low pK with special relevance to human semen: passive pH regulation.
1. The significant difference in pK between phosphorylcholine (PCh) and inorganic phosphate (Pi) of over 1 pH unit results in PCh being a source of acid buffering potential and an actual sink for protons when it is hydrolyzed. Phosphorylethanolamine (PEth) can fill the same role. 2. Both semen and tissues having substantial anaerobic metabolism among which are those of fetal origin can face circumstances of non-pathological acidosis. 3. We demonstrate from the literature that all of those tissues with the two understandable exceptions of erythrocytes and striated muscle, have high levels of PEth and/or PCh. 4. Since these phosphomonoesters can serve as lipid metabolites as well as low-pK fixed-phosphate buffer it appears they can serve a dual function in these tissues. 5. Their concentration would vary depending on the physiological and biochemical conditions present and we would call this a "Swiss army knife" theory of metabolic function.
Burt
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CT
Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
Chen
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B
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002794:Choline / Q000031:analogs & derivatives*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D010767:Phosphorylcholine / Q000378:metabolism*; D012661:Semen / Q000378:metabolism*
D010767:Phosphorylcholine; D000469:Alkaline Phosphatase; D002794:Choline