An alternative pathway for nitric oxide production in plants: new features of an old enzyme.

compounds, the identification of the cofactor in the AOs was not an easy task, involving derivatization of the enzyme-bound cofactor with carbonyl reagents to form a stable adduct, followed by detailed characterization of active site cofactor-containing peptides using spectroscopy, mass spectroscopy and NMR (Ref. 9). Consistent with these advances on AOs and related quinoproteins, the possibility that PQQ or a closely related quinonoid compound (such as TPQ) might be bound at the CKO active site has recently been addressed.