Calcium-dependent inactivation of neuronal nitric oxide synthase: evidence for the existence of stabilization / activation factor

Biochem Biophys Res Commun. 1997 May 19;234(2):476-80. doi: 10.1006/bbrc.1997.6664.


Neuronal nitric oxide synthase (nNOS; EC activity in supernatant of rat cerebellum homogenate was unstable and chelating reagent protected the activity from the rapid decrease. The main target ion of the chelating reagent was found to be Ca2+. Although the enzyme was very unstable after purification by the procedures including DEAE-cellulose chromatography and ammonium sulfate precipitation, the inactivation was neither accelerated by addition of Ca2+ nor protected by EGTA. Upon addition of boiled supernatant of rat cerebellum homogenate, this purified enzyme became more active and stable, but rapid inactivation occurred again by addition of Ca2+, suggesting the existence of previously unreported Ca2(+)-dependent stabilizer / activator in the boiled supernatant. This factor was concentrated by organic solvent and the effects on the enzyme were completely canceled by addition of Ca2+ or phospholipase C treatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium / pharmacology*
  • Cerebellum / enzymology
  • Chelating Agents / pharmacology
  • Egtazic Acid / pharmacology
  • Enzyme Activation
  • Enzyme Inhibitors / metabolism
  • Enzyme Inhibitors / pharmacology*
  • Enzyme Stability
  • In Vitro Techniques
  • Male
  • Neurons / enzymology*
  • Nitric Oxide Synthase / antagonists & inhibitors*
  • Nitric Oxide Synthase / isolation & purification
  • Rats
  • Rats, Wistar
  • Type C Phospholipases / pharmacology


  • Chelating Agents
  • Enzyme Inhibitors
  • Egtazic Acid
  • Nitric Oxide Synthase
  • Type C Phospholipases
  • Calcium