A comparative study of 5'nucleotidase and alkaline phosphatase in human placenta during development.

Activities and a few properties of alkaline phosphatase and 5′-nucleotidase were compared in the developing human placenta. Both the enzymes were mostly membrane-bound and displayed similar developmental patterns with the highest activities at 24/26 weeks of the placenta. L-Phenylalanine, L-tryptophan and L-leucine were inhibitors of alkaline phosphatase, whereas they had no effect on the 5′-nucleotidase. Alkaline phosphatase from a late stage of gestation appeared to be almost heat-stable. An appreciable part of 5′-nucleotidase was also resistant to heat inactivation and this fraction varied with gestational age of the tissue. For both the enzymes, Vmax changed without altering Km values with periods of gestation. Ca2+ , Mg2+ and Mn2+ ions stimulated the alkaline phosphatase activity and Hg2+ , Zn2+ , Cu2+ ,Ni2+ were inhibitory. 5′-Nucleotidase was not activated by any of these cations. EDTA and Concanavalin A inhibited both the enzymes, although the extent of inhibition was different and also varied with gestation.