Cyclic AMP dependent protein kinase in human placenta.

There have been few reports on cyclic AMP dependent protein kinase in the human placenta. As our first study on this enzyme we here report the confirmation of its existence in human placental chorion and its chemical characteristics and the measured activities of the enzyme in each gestational trimester. 1. Chemical characteristics: (1) pH Profile: Maximum specific activity was found to be between pH7.5 and 8.5. (2) Effects of Mg2+: Magnesium ions activated protein kinase activity. Maximum specific activity was found to be 5mM. (3) Km for ATP: Km was found to be 4.94 microM. 2. Activity of cyclic AMP dependent protein kinase of human placental chorion in each gestational trimester: The specific activities (p moles ATP/mg protein/minute) of each gestational trimester were 44.67 +/- 5.29 for the first, 45.24 +/- 9.13 for the second and 34.19 +/- 4.95 for the third trimester. There was a significantly lower value in the third trimester (t less than 0.001), compared to the first and second trimester.