Abstract: Assays and methods for detecting and quantifying the activity of a test kinase. The assay includes a nucleotide phosphatase at least ten times more active on ADP than on ATP and a free phosphate detector. The assay may also include a control kinase and/or ATP. Methods of the invention include combining a test kinase, a substrate of the test kinase, and a known quantity of ATP under conditions to produce ADP, combining the produced ADP with a phosphatase specific for ADP, and measuring free phosphate. The amount of phosphate produced directly correlates to the activity of the kinase.

Abstract: A kit for detecting or measuring glycosyltransferase activity including a first reagent comprising a phosphatase and a second reagent comprising a free phosphate detector, and method of detecting and measuring glycosyltransferase activity. A sugar donor, an acceptor substrate, a glycosyltransferase enzyme and a phosphatase are combined and the amount of free phosphate present in the product is measured and used to calculate the activity of the glycosyltransferase enzyme.

Abstract: Assays and methods for detecting and/or quantifying activity of a test sulfotransferase comprising by releasing a free phosphate from the PAP produced by the sulfotransferase reaction and detecting the free phosphate. The assay can includes gPAPP, a free phosphate detector and an optional control sulfotransferase. The method includes combining a test sulfotransferase with the substrate of the sulfotransferase, PAPS and gPAPP and detecting the free phosphate. The level of free phosphate directly correlates to the activity of the sulfotransferase. The assay and methods can be used to screen agents for their effect upon sulfotransferase activity.