Parathyroid Hormono-hydrolyzing Enzymes in Human Kidney

Abstract

Human kidney tissue obtained at autopsy was homogenized in 0.15M KCl and centrifuged at 600 or 100, 000g to test the supernatants for the activity of hydrolyzing ¹²⁵Ilabelled bovine parathyroid hormone through incubation at 37°C for 1 hour and measurement of trichloroacetic acid-soluble ¹²⁵I released. PTH-hydrolyzing activity was apparently soluble and mainly located in the supernatant fraction of centrifugation at 100, 000 with the optimal pH of 4.5, unlike the rat kidney microsomal parathyroid hormone-hydrolyzing enzyme with optimal pH of 8.5. The activity per unit tissue weight slightly increased with advance in age but the total activity in both kidneys decreased with advance in age.