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 extra cted from neutral supernatants by CHCl3/MeOH (2:1 or 1:1). It partitio ns into the organic fraction of CHCl4/MeOH extracts, whereas the aqueo us fraction contains a component that potentiates the activator's capa city to stimulate CaM-PDE. The activator interacts with PDE by increas ing its apparent affinity for CaM. Size partition chromatography of CH Cl3/MeOH extracts from spontaneously hypertensive rats produces two ac tivity 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 activ ator behaves as a lipopeptide that shares several characteristics with parathyroid hypertensive factor.