Separation and characterization of a novel isoenzyme of cyclic nucleotide phosphodiesterase from rat cerebrum

Br J Pharmacol. 1994 Feb;111(2):389-90. doi: 10.1111/j.1476-5381.1994.tb14745.x.


Anion-exchange chromatography on a Mono-Q column of the supernatant fraction, after ultracentrifugation, from a homogenate of rat cerebrum, prepared under isotonic conditions in the presence of protease inhibitors, yielded a novel isoenzyme of cyclic nucleotide phosphodiesterase (PDE) with properties unlike those of known PDEs. The isoenzyme was insensitive to stimulation by Ca2+/calmodulin and cyclic GMP, and it hydrolyzed both cyclic AMP and cyclic GMP with KM values of 0.109 +/- 0.008 microM and 1.78 +/- 0.04 microM, respectively. The ratio of Vmax of hydrolysis of cyclic GMP to that of cyclic AMP was 1.90 +/- 0.07. Nicardipine (PDE I inhibitor), SK&F 94120 (PDE III inhibitor), rolipram (PDE IV inhibitor) and zaprinast (PDE V inhibitor) had very weak inhibitory effects on the PDE activity of the isoenzyme. These results suggest that the isoenzyme is a novel and previously unreported species of PDE, which we tentatively designate PDE VIII.

MeSH terms

  • 3',5'-Cyclic-AMP Phosphodiesterases / analysis
  • 3',5'-Cyclic-AMP Phosphodiesterases / antagonists & inhibitors
  • 3',5'-Cyclic-AMP Phosphodiesterases / isolation & purification*
  • Animals
  • Brain / drug effects
  • Brain / enzymology*
  • Calcium / pharmacology
  • Calmodulin / pharmacology
  • Chromatography, Ion Exchange
  • Cyclic AMP / metabolism
  • Cyclic GMP / metabolism
  • Enzyme Activation / drug effects
  • In Vitro Techniques
  • Isoenzymes / analysis
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / isolation & purification*
  • Kinetics
  • Male
  • Molecular Weight
  • Rats


  • Calmodulin
  • Isoenzymes
  • Cyclic AMP
  • 3',5'-Cyclic-AMP Phosphodiesterases
  • Cyclic GMP
  • Calcium