Mammalian O-phosphorylethanolamine phospho-lyase activity and its inhibition

The activity of the enzyme O-phosphorylethanolamine phospho-lyase, metabolizing O-phosphorylethanolamine to acetaldehyde, orthophosphate, and ammonia in vitro, was studied in human liver biopsy and autopsy material, and leucocytes. Only in the liver biopsies enzyme activity towards O-phosphorylethanolamine could be found, and in amounts corresponding to one tenth of the activity found in rat liver examined under identical conditions. The enzyme activity of the liver biopsies was confined to the post-microsomal fraction, the activity amounting to 35 ± 7 (SD) μU/mg protein. The results suggest the presence of an inhibiting factor of protein character. Inhibition was not due to competition from alkaline phosphatase (E.C. 3.1.3.1.) or O-phosphorylethanolamine cytidylyl-transferase (E.C. 2.7.7.14).