Abstract
Methods for assaying serine/threonine protein phosphatases are discussed. Three commonly used protocols are presented that employ either colorimetric or radiometric assays. These methods can be used to assay a variety of preparations of serine/threonine phosphatases, from crude lysates to purified proteins. Strategies for the application of a particular protocol for a particular purpose are discussed. The assays can be used in either a high-throughput mode where simple comparison of activities can be done, or in specific assays where kinetic data can be derived.