UNIT 4.16 Evaluation of the Cytochrome b5/Cytochrome b5 Reductase Pathway

  1. Lauren A. Trepanier,
  2. Sunil U. Bajad,
  3. Joseph R. Kurian

Published Online: 1 JUN 2005

DOI: 10.1002/0471140856.tx0416s24

Current Protocols in Toxicology

Current Protocols in Toxicology

How to Cite

Trepanier, L. A., Bajad, S. U. and Kurian, J. R. 2005. Evaluation of the Cytochrome b5/Cytochrome b5 Reductase Pathway. Current Protocols in Toxicology. 24:4.16:4.16.1–4.16.17.

Author Information

  1. University of Wisconsin–Madison, Madison, Wisconsin

Publication History

  1. Published Online: 1 JUN 2005
  2. Published Print: MAY 2005


NADH cytochrome b5 reductase (b5R; EC; Diaphorase I; NADH: ferricytochrome b5 oxidoreductase) is an FAD-containing protein, which, along with the hemoprotein cytochrome b5 (cyt b5), mediates electron transfer from NADH to fatty acid desaturases, P450 oxidases, methemoglobin, and ascorbyl free radical. In addition, b5R and cyt b5 can directly catalyze the reduction of hydroxylamine and amidoxime metabolites. This unit provides protocols for measuring the activity and mRNA expression of the cytochrome b5/cytochrome b5 reductase pathway, and for obtaining heterologous expression and purification of the soluble forms of each protein.


  • Cytochrome b5 reductase;
  • cytochrome b5;
  • hydroxylamine;
  • ferrihemoglobin reduction;
  • qRT-PCR;
  • protein purification