Four distinct human isoenzymes of alkaline phosphatase (AP) are known: intestinal (IAP), placental (PLAP), tissue non-specific (NSAP, also known as liver/bone/kidney AP), and germ cell AP (also known as placental-like AP, PLAP-like). L-p-Bromotetramisole is a cell-permeable inhibitor of all four human AP isoenzymes (Kis =18 and 56 μM for PLAP and NSAP, respectively). While PLAP is strongly inhibited by L-p-bromotetramisole, a second AP, possibly PLAP-like, shows only partial inhibition. L-p-Bromotetramisole has been shown to inhibit a tyrosine phosphatase from Drosophila and, as a result, is also used as a tyrosine phosphatase inhibitor.
