Alkaline Orthophosphatase and Inorganic Pyrophosphatase Activities in Human Serum

Abstract

IT has been found that alkaline phosphatase from human and animal tissues can hydrolyse inorganic pyrophosphate^1–3, contrary to earlier reports that these enzymes act solely on organic orthophosphates. A consequence of this suggested broader specificity is that the concentration of inorganic pyrophosphatase in human blood serum should parallel the well known variations in alkaline phosphatase activity observed in diseases of the skeleton and the hepatobiliary system, if the two types of substrate are indeed hydrolysed by a single enzyme. We have therefore determined the activities of alkaline orthophosphatase and inorganic pyrophosphatase by the methods of Moss et al.² in seventy-one specimens of human blood serum on which alkaline phosphatase estimations were requested for diagnostic purposes. The sera were classified into fifty-two from cases of hepatobiliary disease (infective hepatitis, obstructive jaundice, and biliary and portal cirrhosis), and nineteen from patients with osteoblastic bone disease (Paget's disease, hyperparathyroidism, and skeletal metastases), on the basis of clinical history and biochemical, radiological and other investigations.