A rapid and precise assay for calmodulin and cyclic AMP phosphodiesterase on a centrifugal analyser

An assay for cyclic AMP phosphodiesterase in biological samples is described. The method is a continuous, spectrophotometric assay adapted for use on a centrifugal analyser. Using the calmodulin-activated cyclic AMP phosphodiesterase prepared from pig brain by DEAE-cellulose chromatography, and a standard calmodulin preparation from the same source, a rapid assay for calmodulin is described. The calmodulin assay has a working range of 2 to 6 mg/l calmodulin in the sample. The within-batch CV is less than 5% and the between-batch CV is 7.0% or less.