Identification and characterization of nitric oxide synthase in Salmonellatyphimurium

The presence of the nitric oxide synthase (NOS) enzyme from Salmonella typh imurium (S. typhimurium) was identified by measuring radiolabeled L-[H-3]ci trulline and NO, and Western blot analysis. NOS was partially purified by b oth Mono Q ion exchange and Superose 12HR size exclusion column chromatogra phy, sequentially. The molecular weight of NOS was estimated to be 93.3 kDa by Western blot analysis. The enzyme showed a significant dependency on th e typical NOS cofactors; an apparent Km for L-arginine of 34.7 mM and maxim um activity between 37 degrees C and 43 degrees C. The activity was inhibit ed by NOS inhibitors such as aminoguanidine and N-G,N-G-dimethyl L-arginine . Taken together, partially purified NOS in S. typhimurium is assumed to be a different isoform of mammalian NOSs.