NADH:Fe(III)-chelate reductase of maize roots is an active cytochrome b5 reductase

FEBS Lett. 1997 Sep 15;414(3):571-5. doi: 10.1016/s0014-5793(97)01073-9.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Membrane / enzymology
  • Cytochrome Reductases / metabolism*
  • Cytochrome-B(5) Reductase
  • Enzyme Inhibitors / pharmacology
  • FMN Reductase*
  • Ferric Compounds / metabolism
  • Fluorometry
  • Hydroxymercuribenzoates / pharmacology
  • Kinetics
  • Microsomes / chemistry
  • Microsomes / enzymology
  • NAD / metabolism
  • NADH, NADPH Oxidoreductases / chemistry
  • NADH, NADPH Oxidoreductases / drug effects
  • NADH, NADPH Oxidoreductases / metabolism*
  • Organomercury Compounds / pharmacology
  • Plant Roots / enzymology*
  • Zea mays / enzymology*

Substances

  • Enzyme Inhibitors
  • Ferric Compounds
  • Hydroxymercuribenzoates
  • Organomercury Compounds
  • NAD
  • 4-hydroxymercuribenzoate
  • ferric citrate
  • FMN Reductase
  • NADH, NADPH Oxidoreductases
  • Cytochrome Reductases
  • Cytochrome-B(5) Reductase
  • ferric citrate iron reductase