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

TLDR: Alkaline phosphatase from a late stage of gestation appeared to be almost heat-stable and an appreciable part of 5’-nucleotidase was also resistant to heat inactivation and this fraction varied with gestational age of the tissue.

Abstract: 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 alteringK m 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.