L-Phenylalanine : an Organ Specific, Stereo-specific Inhibitor of Human Intestinal Alkaline Phosphatase

Alkaline phosphatase activity associated to a calcium binding glycoprotein from calf scapula cartilage

“…L-Phenylalanine is considered an organo-specific and stereo-specific inhibitor of the intestine alkaline phosphatase [19]. On the contrary, phosphatases of tissue different from intestine, are insensitive to this L-amino acid [20]. The enzymatic activity of our preparation also is not influenced by 5 mM L-phenylalanine.…”

Gly429 is the major determinant of uncompetitive inhibition of human germ cell alkaline phosphatase by l-leucine

“…Whereas the three TSAP isozymes display more than 90 % sequence identity, they share only 50 % similarity with the TNAP isoenzyme. The three TSAP isoenzymes are equally inhibited by L-Phe but not by L-homoarginine or by the other TNAP-specific inhibitors (Fishman & Sie, 1971;Fishman et al, 1963;Mulivor et al, 1978). Furthermore, GCAP is selectively inhibited by L-Leu (Doellgast & Fishman, 1976).…”

Serum alkaline phosphatase in hypophosphatasia

“…It has been shown that 5 mm l-phenylalanine in the assay inhibits intestinal alkaline phosphatase 77% whereas the d-isomer is without effect (11). A measure of the intestinal contribution to the total serum alkaline phosphatase is obtained by substracting the values obtained with l-phenylalanine in the assay from the total alkaline phosphatase (in the presence of d-phenylalanine) activity (12). Heat sensitivity of serum alkaline phosphatase is determined by heating the samples for 16 min at 55'C in a circulating water bath (5).…”