IN-VIVO INACTIVATION OF PHOSPHOTYROSINE PROTEIN PHOSPHATASES BY NITRIC-OXIDE

The effect of NO on phosphotyrosine protein phosphatases (PTPases) has been investigated in vivo. NO production is induced in interferon-gam ma and lipopolyaccharide stimulated RAW-263.7 macrophages as indicated by the increase of NO2- in the medium, Our results demonstrate an inh ibition of p-nitrophenylphosphatase activity as a consequence of macro phages activation, Under the described experimental conditions, most o f the hydrolysis of p-nitrophenylphosphate can be ascribed to the acti on of cellular PTPases. The presence of N-G-monomethyl-L-arginine, a s pecific inhibitor of NO synthase decreases the inactivation rate of bo th membrane-bound and soluble PTPases. This evidence further confirms the ability of NO to inactivate PTPases and suggests a possible role o f NO in the regulation of cellular processes involving this class of p hosphatases.