The inducible alkaline phosphatase of rat heart: Partial purification of the enzyme and its substrate specificity

The activity of an alkaline phosphatase in the right atrium of rat heart is enhanced by administration of catecholamines or their analogues. The enzyme has been partially purified from the atria of isoproterenol-treated animals and its substrate specificity has been investigated. It hydrolyses inorganic pyrophosphate and ATP besides orthophosphates such as p-nitrophenyl phosphate and β-glycerophosphate. Between pH 7 and 8, the rates of hydrolysis of inorganic pyrophosphate and p-nitrophenyl phosphate are similar, whereas at more alkaline pH values orthophosphatase activity predominates. The ratio of activities of the atrial phosphatase towards various substrates resembles that for analogous enzymes from other vertebrate tissues such as liver or kidney.