Function of calmodulin in mammalian sperm: presence of a calmodulin-dependent cyclic nucleotide phosphodiesterase associated with demembranated rat caudal epididymal sperm

Biochem Biophys Res Commun. 1984 Jan 30;118(2):636-42. doi: 10.1016/0006-291x(84)91350-0.


A calmodulin dependent cyclic nucleotide phosphodiesterase is associated with the head and tailpieces of demembranated rat caudal epididymal sperm. The phosphodiesterase was stimulated two-fold in the presence of Ca2+, while the simultaneous addition of Ca2+ and calmodulin resulted in a four-fold increase in activity. Ca2+ stimulation was abolished if demembranated sperm were extracted with EGTA and was recovered upon the addition of exogenous calmodulin. Micromolar levels of Ca2+ were required for full stimulation. Trifluoperazine inhibited the Ca2+ stimulated enzyme in a dose dependent manner (ID50 = 50 microM) but had no effect on the basal phosphodiesterase activity.

MeSH terms

  • 3',5'-Cyclic-AMP Phosphodiesterases / metabolism
  • Animals
  • Calcium / pharmacology
  • Calmodulin / pharmacology
  • Calmodulin / physiology*
  • Cell Membrane / enzymology
  • Cyclic Nucleotide Phosphodiesterases, Type 1
  • Cytosol / enzymology
  • Egtazic Acid / pharmacology
  • Epididymis
  • Kinetics
  • Male
  • Rats
  • Rats, Inbred Strains
  • Spermatozoa / enzymology*
  • Trifluoperazine / pharmacology


  • Calmodulin
  • Trifluoperazine
  • Egtazic Acid
  • 3',5'-Cyclic-AMP Phosphodiesterases
  • Cyclic Nucleotide Phosphodiesterases, Type 1
  • Calcium