5′-Nucleotidase in the Detection of Increased Activity of the Liver Form of Alkaline Phosphatase in Serum

Abstract

5′-Nucleotidase (5′-ribonucleotide phosphohydrolase; EC 3.1.3.5; 5NT), an intrinsic membrane glycoprotein present as an ectoenzyme in a wide variety of mammalian cells, hydrolyzes 5′-nucleotides to their corresponding nucleosides (1). Despite its ubiquitous distribution, serum concentrations of 5NT appear to reflect hepatobiliary disease with considerable specificity (2). Dixon and Purdom (3) first observed that serum 5NT was clinically useful for differential diagnosis of hepatobiliary and osseous diseases, the enzyme activity being increased only in hepatobiliary diseases. This finding has been confirmed by several authors (4)(5)(6)(7). Assay of 5NT activity may have value as an addition to measurement of nonspecific total alkaline phosphatase (AP) in patients with suspected hepatobiliary disease (8)(9)(10)(11)(12), and abnormal 5NT activity is routinely interpreted by some clinicians as evidence of a hepatic origin of increased AP activity in serum. However, a direct comparison of 5NT and the liver form of AP (L-AP) in a clinical setting has not been reported (13). The aim of this …