J. Mukai et al., SEPARATION AND CHARACTERIZATION OF A NOVEL ISOENZYME OF CYCLIC-NUCLEOTIDE PHOSPHODIESTERASE FROM RAT CEREBRUM, British Journal of Pharmacology, 111(2), 1994, pp. 389-390
Anion-exchange chromatography on a Mono-Q column of the supernatant fr
action, after ultracentrifugation, from a homogenate of rat cerebrum,
prepared under isotonic conditions in the presence of protease inhibit
ors, yielded a novel isoenzyme of cyclic nucleotide phosphodiesterase
(PDE) with properties unlike those of known PDEs. The isoenzyme was in
sensitive to stimulation by Ca2+/calmodulin and cyclic GMP, and it hyd
rolyzed both cyclic AMP and cyclic GMP with KM values of 0.109 +/- 0.0
08 mu M and 1.78 +/- 0.04 mu M, respectively. The ratio of V-max of hy
drolysis of cyclic GMP to that of cyclic AMP was 1.90 +/- 0.07. Nicard
ipine (PDE I inhibitor), SK&F 94120 (PDE III inhibitor), rolipram (PDE
IV inhibitor) and zaprinast (PDE V inhibitor) had very weak inhibitor
y 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.