NucleotidePyrophosphataseand Phosphodiesterase.I. Organ Distributionand Activitiesin Body Fluids

We estimated nucleotide pyrophosphatase and phos-phodiesterase I activities in human and rat organs and in body fluids from man and dog. The highest organ activities were found in epididymis, kidney, liver, and intestine. In body fluids, the activity was highest in seminal plasma, followed by intestinal lymph, serum, heart lymph, cere-brospinal fluid, milk, and urine. The ratio nucleotide pyro-phosphatase/phosphodiesterase I and the urea resistance of phosphodiesterase I differed among human organs, body fluids, and blood cells. Different isoenzymes probably exist. The activities in serum share several properties with those in several organs-e.g., pH-optimum 9.6-9.8, dependency on Zn2, and the effects of inhibitors. Phosphodiesterase I in erythrocytes, which has not been described previously, differs from enzyme from other sources by lower pH op-timum (8.5), dependency on Mg2, inhibition by Zn2, and stimulation by dithiothreitol. AddItIonal Keyphrases: man, rats, dogs. activity in seminal plasma, blood cells, cerebrospinal fluid, serum, bile, intestinal lymph, milk, urine, heart lymph- inhibition by urea. cation co-factors (activators). possible transport function Nucleotide pyrophosphatase (EC 3.6.1.9) activity (1) and phosphodiesterase I (EC 3.1.4.1) activity (1-3) were recently demonstrated in normal human serum. Both activities are probably attributable to one enzyme (1, 4-6). An increase of the activities in serum was found in cholestatic liver disease and in cancer with bone metastases (1, 2). The clinical importance of determi-nations of this enzyme in body fluids remains to be es-tablished, however. The present study on the organ distribution of the enzyme and its activity in body fluids was performed to provide a basis for clinical applications