Biochemical characteristics of a calmodulin-phosphodiesterase activator increased in spontaneously hypertensive mice and rats.

The biochemical characteristics of calmodulin-phosphodiesterase (CaM-PDE) are described. It is a cytosolic, hydrophobic, and heat-, acid-, and base-stable compound sensitive to proteases. It is optimally extracted from neutral supernatants by CHCl3/MeOH (2:1 or 1:1). It partitions into the organic fraction of CHCl3/MeOH extracts, whereas the aqueous fraction contains a component that potentiates the activator's capacity to stimulate CaM-PDE. The activator interacts with PDE by increasing its apparent affinity for CaM. Size partition chromatography of CHCl3/MeOH extracts from spontaneously hypertensive rats produces two activity peaks, one eluting at void volume with the second eluting at a position corresponding to a 4-kDa peptide. The compound at void volume can be converted to the 4-kDa entity by sonication. The CaM-PDE activator behaves as a lipopeptide that shares several characteristics with parathyroid hypertensive factor.