PROPERTIES OF ACTIVITY OF 5'-NUCLEOTIDASE IN HUMAN SERUM, AND APPLICATIONS IN DIAGNOSIS

Simultaneous determination of 5'-nucleotidase and alkaline phosphatase activities in serum

A simple method is described for the simultaneous determination of alkaline phosphatase (EC 3.1.3.1) and 5'-nucleotidase (EC 3.1.3.5) in serum. The method is based on the determination of inorganic phosphorus released by the action of the two enzymes on adenosine-5'-monophosphate at pH 9.5 (200 mmol/l tris-buffer) in the presence and absence of L-cysteine. This amino acid at a concentration of 2--10 mmol/l was found to be a specific inhibitor for alkaline phosphatase but with no effect on 5'-nucleotidase activity.

Activation of serum 5' nucleotidase by magnesium ions and its diagnostic applications

Magnesium ions increase the hydrolysis of adenosine 5' monophosphate (5' AMP) by human serum at pH 7.9 but not at pH 9.3. The additional hydrolysis at pH 7.9 is predominantly due to increased activity of the specific phosphatase 5' nucleotidase (5Nase). This increase is proportional to enzyme concentration and has been employed as a measure of 5Nase activity in a sensitive micro-estimation. The normal range for serum 5Nase activity by this technique was 0 to 20 mIU/ml. In a series of over 200 patients, raised values were found frequently in hepatobiliary disease and infrequently in bone disease. Assay of 5Nase activity gave a more reliable indication of the source of raised serum alkaline phosphatase than isoenzyme electrophoresis in agar gel. The correlation between activities of the two enzymes was low in bone disease generally, and fairly good in hepatobiliary disease. The closest correlation was found in patients with parenchymal liver disease.