5'-Nucleotide phosphodiesterase isoenzymes in human serum: quantitative measurement and some biochemical properties.

A method based on native PAGE is used for the quantitative measurement of 5'-nucleotide phosphodiesterase isoenzymes (5'-NPD; EC 3.1.4.1) in human serum. In contrast to other techniques this method works with a commercially available substrate. In sera of healthy donors four isozymes could be separated, designated as 5'-NPD-I, 5'-NPD-II, 5'-NPD-III and 5'-NPD-IV in the reverse order of their electrophoretic mobility. When low amounts of serum were applied to the gel, the separation between all four activities was sufficient enough to allow their quantitation. Higher amounts of serum impaired the separation between the isoenzymes I and II. However, even when using high amounts of serum, the quantitation of these activities was possible when taking advantage of some of their biochemical properties which are described herein.