A calcineurin-like phosphatase is required for catch contraction.

The ability of certain molluscan smooth muscles to maintain a prolonged state of contraction, termed 'catch', has been correlated with the activity of a calcineurin-like Ca(2+)-regulated phosphatase. The release of this phosphatase through extensive treatment of fibers with detergent, as shown by Western blots and a calmodulin-binding overlay assay, results in the loss of catch tension maintenance. This effect is reversed by perfusion of the fiber with brain calcineurin. These findings suggest that the activity of the calcineurin-like phosphatase, switched on during the onset of active contraction, plays a critical role in the maintenance of catch.