Comparative rates of metabolism of pipecolic acid in several animal species.

1. The rate of metabolism of pipecolic acid, measured in liver and kidney, varied 1000 fold among 10 animal species. Degradation of L-pipecolic acid by kidney in rat and mouse was 0.11 and 0.31 pmoles/min/mg protein, respectively; in monkey and human. 3.0 and 6.5; in guinea-pig and rabbit 101 and 106. 2. Activity with D-pipecolic acid was consistently 50-60% higher than the L-isomer except in the rabbit. 3. Degradation of L-lysine presumably through the saccharopine-alpha-aminoadipic acid pathway, was effective in all species, contrasting with the variable performance in the pipecolic acid-alpha-aminoadipic acid pathway.