A possible new locus of alkaline phosphatase expressed in human testis

Human testes contain trace amounts of heat-stable placental-like alkaline phosphatase. Using a recently described allotype-specific monoclonal antibody (F11) toward placental alkaline phosphatase (PLAP), we show that the frequencies of reactivity of the testis enzymes differ greatly from those of the placental phenotypes. By means of the enzyme inhibitors L-Phe, L-Phe-gly-gly, L-Leu, and L-Leu-gly-gly, the testis enzyme can be clearly distinguished in all cases from the placental enzyme. These results argue that the testis enzyme is not a product of the placental gene and suggest the possible existence of a new locus of alkaline phosphatase.