NADH:Fe(III)-chelate reductase of maize roots is an active cytochrome b5 reductase.
Microsomal NADH:Fe(III)-chelate reductase (NFR) of maize roots has been purified as a monomeric flavoprotein of 32 kDa with non-covalently bound FAD. In the presence of NADH, NFR efficiently reduced the physiological iron-chelate Fe(III)-citrate (K[cat]/K[m](Fe(III)-citrate) = 6.0 X 10[6] M[-1] S[-1]) with a sequential reaction mechanism. Purified NFR was totally inhibited by the sulfhydryl reagent PHMB at 10(-9) M, and it could use cyt b5 as alternative electron acceptor with a maximal reduction rate as high as with Fe(III)-citrate. We conclude that in maize roots the reduction of Fe(III)-citrate is chiefly performed by a cytochrome b5 reductase, mostly associated with intracellular membranes and in part with the plasma membrane.
Sparla
F
F
Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, Italy.
Bagnaresi
P
P
Scagliarini
S
S
Trost
P
P
D002462:Cell Membrane / Q000201:enzymology; D003579:Cytochrome Reductases / Q000378:metabolism*; D042966:Cytochrome-B(5) Reductase; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038181:FMN Reductase; D005290:Ferric Compounds / Q000378:metabolism; D005470:Fluorometry; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D007700:Kinetics; D008861:Microsomes / Q000737:chemistry / Q000201:enzymology; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D009941:Organomercury Compounds / Q000494:pharmacology; D018517:Plant Roots / Q000201:enzymology*; D003313:Zea mays / Q000201:enzymology*
D004791:Enzyme Inhibitors; D005290:Ferric Compounds; D006902:Hydroxymercuribenzoates; D009941:Organomercury Compounds; D009243:NAD; C030601:4-hydroxymercuribenzoate; C025314:ferric citrate; D038181:FMN Reductase; D009247:NADH, NADPH Oxidoreductases; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; C023903:ferric citrate iron reductase