HIGHLY EFFICIENT CONTROL OF IRON-CONTAINING NITRILE HYDRATASES BY STOICHIOMETRIC AMOUNTS OF NITRIC-OXIDE AND LIGHT

The reaction of two iron-containing nitrile hydratases (NHase) with NO has been studied: NHase from Rhodococcus sp. R312, which is probably similar to the photosensitive N771 NHase, and the new NHase from Comam onas testosteroni NI1 whose aminoacid sequence is quite different from those of BR312 and N771 NHases. Both enzymes are equally inactivated after addition of stoichiometric amounts of NO added as an anaerobic s olution or produced in situ under physiological conditions by a rat br ain NO-synthase. Both enzymes are reactivated by photoirradiation, and two cycles of NO inactivation/photoactivation can be performed withou t significant loss of activity. Both iron-containing NHases have a hig h affinity for NO, similar to that of methemoglobin. (C) 1997 Federati on of European Biochemical Societies.