A class of enzymes present in various organs and in many cells that catalyze the hydrolysis of a 5'-ribonucleotide to a ribonucleoside and orthophosphate in the presence of water. Serum 5'-N'Tase is measured as an indicator of liver damage resulting primarily from interference with the secretion of bile. Serum 5'-N'Tase is not as sensitive as some other enzymes (for example, ALP, AST, and ALT) to liver damage, but it is a more liver-specific enzyme. The level of this enzyme parallels alkaline phosphatase (ALP). It is used mostly to differentiate elevations in the above enzymes due to liver damage from damage to skeletal muscle. [ ]