title: Function of calmodulin in mammalian sperm: presence of a calmodulin-dependent cyclic nucleotide phosphodiesterase associated with demembranated rat caudal epididymal sperm.
abstract: 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: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000494:pharmacology / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D003600:Cytosol / Q000201:enzymology; D004533:Egtazic Acid / Q000494:pharmacology; D004822:Epididymis; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013094:Spermatozoa / Q000201:enzymology*; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D014268:Trifluoperazine; D004533:Egtazic Acid; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054677:Cyclic Nucleotide Phosphodiesterases, Type 1; D002118:Calcium