THE PROTEIN INHIBITOR OF NEURONAL NITRIC-OXIDE SYNTHASE (PIN) - CHARACTERIZATION OF ITS ACTION ON PURE NITRIC-OXIDE SYNTHASES

Neuronal NO synthase (nNOS) was discovered recently to interact specif ically with the protein PIN (protein inhibitor of nNOS) [Jaffrey S.R. and Snyder S.H. (1996) Science 274, 774-777]. We have studied the effe cts on pure NOS enzymes of the same GST-tagged PIN used in the origina l paper, Unexpectedly, all NOS isoenzymes were inhibited. The IC50 for nNOS was 18 +/- 6 mu M GST-PIN with 63 nM nNOS after 30 min at 37 deg rees C, Uncoupled NADPH oxidation was inhibited similarly, whereas cyt ochrome c reductase activity, the K-M for L-arginine, and dimerization were unaffected. We reconsider the physiological role of PIN in the l ight of these results. (C) 1998 Federation of European Biochemical Soc ieties.