CLONING, CHARACTERIZATION, AND EXPRESSION OF A CDNA-ENCODING AN INDUCIBLE NITRIC-OXIDE SYNTHASE FROM THE HUMAN CHONDROCYTE

Incubation of human articular chondrocytes with interleukin 1beta resu lts in the time-dependent expression of nitric oxide (NO) synthase. We report here the isolation of a cDNA clone which encodes a protein of 1153 amino acids with a molecular mass of 131,213 Da and a calculated isoelectric point of 7.9. CHO cells transfected with a plasmid harbori ng this cDNA clone expressed NO synthase activity that was inhibited b y some L-arginine analogues. The deduced amino acid sequence of the hu man chondrocyte inducible NO synthase shows 51% identity and 68% simil arity with the endothelial NO synthase and 54% identity and 70% simila rity with the neuronal NO synthase. The similarity (88%) between the h uman chondrocyte NO synthase cDNA sequence and that reported for the m urine macrophage suggests that the inducible class of enzyme is conser ved between different cell types and across species.