Inorganic pyrophosphatase activity of the synovial fluid. Kinetic and clinical study.

Inorganic pyrophosphatase activity has been partially characterized in joint fluid and determined in patients with sporadic and familial chondrocalcinosis and their controls. Optimal pH was established at 3.5 and Km values were estimated. Ca-2 and Mg-2 did not affect this activity whereas orthophosphate (Pi) strongly inhibited it. In the clinical study no significant differences were found among groups. This suggests that if a pyrophosphatase defect is present it might be localized in joint tissue and not be reflected in synovial fluid.