Citrulline is not the major product using the standard "NOS activity" assay on renal cortical homogenates.

@article{Conrad2002CitrullineIN,
  title={Citrulline is not the major product using the standard "NOS activity" assay on renal cortical homogenates.},
  author={Kirk P. Conrad and Robert William Powers and Alan K Davis and Jackie Novak},
  journal={American journal of physiology. Regulatory, integrative and comparative physiology},
  year={2002},
  volume={282 1},
  pages={R303-10}
}
A standard approach to assessing nitric oxide synthase (NOS) activity in tissue homogenates is 1) removal of small-molecular-weight substances by size-exclusion chromatography, 2) adding back of substrates/cofactors in precise concentrations with a radioactive isotope of arginine (Arg), and 3) quantification of labeled citrulline (Cit) after separation of… CONTINUE READING