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Clinical Chemistry 21: 1383-1387, 1975;
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Clinical Chemistry, Vol 21, 1383-1387, Copyright © 1975 by the American Association for Clinical Chemistry

Determination of Phosphodiesterase I Activity in Human Blood Serum

Ivo Hynie 1, Mary Meuffels 1, and Wojciech Janusz Poznanski 1

1 Division of Biochemistry, Department of Laboratory Medicine, Ottawa Civic Hospital, 1053 Carling Ave., Ottawa, Ontario, Canada K1Y 4E9.

Phosphodiesterase I (EC 3.1.4.1) activity was detected in normal human blood serum. The enzyme is stable at laboratory temperature for three days, but is inactivated at pH <7. The pH for optimum activity increases with the substrate concentration (under the conditions used, from pH 9.0 to 10.2) and, conversely, the Km increases with pH and buffer concentration. The enzyme is inhibited by ethylenediaminetetraacetate but not by phosphate (0.1 mol/liter). We developed a simple quantitative method for its determination, based on hydrolysis of the p-nitrophenyl ester of thymidine 5'-monophosphate and subsequent measurement of the liberated p-nitrophenol at 400 nm in NaOH (0.1 mol/liter). Normal values (mean ± 2 SD) were determined to be 33 ± 6.4 U/liter. Preliminary studies indicate that phosphodiesterase I activity is greater than normal in serum of patients with necrotic changes in the liver or kidney or in cases of breast cancer, but not in that of patients with myocardial infarction, bone cancer, lung cancer, or chronic liver cirrhosis.


Key Words: enzyme activity • spectrophotometry • cancer • heart disease • liver disease • normal (reference) values • relation to alkaline phosphatase activity

Submitted on July 30, 1974
Accepted on June 6, 1975




The following articles in journals at HighWire Press have cited this article:


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 J. Biol. Chem.Home page
H. Sakagami, J. Aoki, Y. Natori, K. Nishikawa, Y. Kakehi, Y. Natori, and H. Arai
Biochemical and Molecular Characterization of a Novel Choline-specific Glycerophosphodiester Phosphodiesterase Belonging to the Nucleotide Pyrophosphatase/Phosphodiesterase Family
J. Biol. Chem., June 17, 2005; 280(24): 23084 - 23093.
[Abstract] [Full Text] [PDF]


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Copyright © 1975 by the American Association for Clinical Chemistry.