title: Studies on the regulation of assimilatory nitrate reductase in Ankistrodesmus braunii.
abstract: In the green alga Ankistrodesmus braunii, all the activities associated with the nitrate reductase complex (i.e., NAD(P)H-nitrate reductase, NAD(P)H-cytochrome c reductase and FMNH2-or MVH-nitrate reductase) are nutritionally repressed by ammonia or methylamine. Besides, ammonia or methylamine promote in vivo the reversible inactivation of nitrate reductase, but not of NAD(P)H-cytochrome c reductase. Subsequent removal of the inactivating agent from the medium causes reactivation of the inactive enzyme. Menadione has a striking stimulation on the in vivo reactivation of the inactive enzyme. The nitrate reductase activities, but not the diaphorase activity, can be inactivated in vitro by preincubating a partially purified enzyme preparation with NADH or NADPH. ADP, in the presence of Mg(2+), presents a cooperative effect with NADH in the in vitro inactivation of nitrate reductase. This effect appears to be maximum at a concentration of ADP equimolecular with that of NADH.
authors.affiliation: Departamento de Bioquímica, Facultad de Ciencias y CSIC, Universidad de Sevilla, Sevilla, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Diez
authors.forename: A
authors.initials: A
authors.lastname: Chaparro
authors.forename: J M
authors.initials: JM
authors.lastname: Vega
authors.forename: A
authors.initials: A
authors.lastname: Relimpio