Studies on human phenylalanine Mono-oxygenase. I. Restricted expression.

Enzyme assays for phenylalanine mono-oxygenase have been performed on a variety of non-hepatic human cell types under varying conditions. The cell types studied were cultured fibroblasts, short-term lymphocyte cultures, long-term lymphoblastoid cultures, cultured amniotic fluid cells, hair roots and placental extracts. The cultured cells were assayed after growth under standard conditions and in the presence of a high concentration of substrate, a low concentration of end-product, added hydrocortisone or dexamethasone and under combinations of these conditions. In no instance was a significant enzyme activity obtained.