Serum 5'-nucleotidase of a breast cancer patient.

Serum derived from the breast cancer patient included in this study was found to be a rich source of 5'-nucleotidase. In addition, it also contains nonspecific alkaline phosphatase. The properties of 5'-nucleotidase were studied by eliminating the interference of serum non-specific alkaline phosphatase by the preliminary incubation of serum in glycine-NaOH buffer containing ethylenediamine tetraacetate and magnesium. The enzyme has a pH optimum at 9.5. It is remarkably stable when held at 50 degrees C at pH 7.5, but it readily lost activity in the acid medium at pH 4.2. It hydrolyzes both the ribo- and deoxyribo-nucleoside 5'-phosphates. It has the highest preference for cytidine 5'-phosphate. Adenosine 2'- or 3'- phosphates are refractory to its action.