Modulation of alkaline phosphatase in different organs by ascorbic acid and related compounds

The organ-specific modulation by ascorbic acid and related compounds on alkaline phosphatase activity of calf intestinal and human placental tissues has been studied at pH 8.0 and 37 degrees C. L(+)-ascorbic acid and its isomer D(-)-ascorbic acid inhibit to a similar extent the intestinal isoenzyme and appear to be more potent modifiers than dehydro-L-(+)-ascorbic acid. In contrast, the placental isoenzyme shows an initial activation by the three chemical agents, followed by an inhibition. The inhibition is lower with L(+)-ascorbic acid and D(-)-ascorbic acid, while its catalytic activity is affected only slightly by dehydro-L-(+)ascorbic acid.