Distribution and contents of free O-phosphoamino acids in animal tissues

This study was carried out to investigate the distribution and contents of O-phosphoserine (P-Ser), O-phosphothreonine (P-Thr), and O-phosphotyrosine (P-Tyr) as their free forms in animal tissues. After extraction of a tissue sample with trichloroacetic acid, these O-phosphoamino acids were converted into their N-isobutoxycarbonyl trimethyl ester derivatives and then quantitated by GLC, with flame photometric detection, on a DB-1701 capillary column. Using this method, nanogram levels of O-phosphoamino acids in tissue samples could be accurately and precisely determined without any interference by coexisting substances. Free P-Ser and P-Thr were widely found in animal tissues, pancreas, spleen, stomach, kidney, liver, and lung containing considerable amounts of these O-phosphoamino acids. On the other hand, free P-Tyr was not detected in any of the tissues investigated in this study.