p40(phox) Participates in the activation of NADPH oxidase by increasing the affinity of p47(phox) for flavocytochrome b(558)

Biochem J. 2000 Jul 1;349(Pt 1):113-7. doi: 10.1042/0264-6021:3490113.


NADPH oxidase is one of the major components of the innate immune system and is used by phagocytes to generate microbicidal reactive oxygen species. Activation of the enzyme requires the participation of a minimum of five proteins, p22(phox), gp91(phox) (together forming flavocytochrome b(558)), p47(phox), p67(phox) and the GTP-binding protein, Rac2. A sixth protein, p40(phox), has been implicated in the control of the activity of NADPH oxidase principally based on its sequence homology to, and physical association with, other phox components, and also the observation that it is phosphorylated during neutrophil activation. However, to date its role in regulating the activity of the enzyme has remained obscure, with evidence for both positive and negative influences on oxidase activity having being reported. Data are presented here using the cell-free system for NADPH oxidase activation that shows that p40(phox) can function to promote oxidase activation by increasing the affinity of p47(phox) for the enzyme approx. 3-fold.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Membrane / metabolism
  • Cell-Free System
  • Cytochrome b Group / metabolism*
  • Cytosol / metabolism
  • Dose-Response Relationship, Drug
  • Enzyme Activation
  • Humans
  • Membrane Glycoproteins / metabolism
  • Membrane Transport Proteins*
  • NADP / metabolism
  • NADPH Dehydrogenase / metabolism
  • NADPH Oxidase 2
  • NADPH Oxidases / metabolism*
  • Neutrophils / metabolism
  • Oxygen / metabolism
  • Phagocytosis
  • Phosphoproteins / metabolism*
  • Protein Binding
  • Recombinant Proteins / metabolism


  • Cytochrome b Group
  • Membrane Glycoproteins
  • Membrane Transport Proteins
  • Phosphoproteins
  • Recombinant Proteins
  • neutrophil cytosol factor 40K
  • neutrophil cytosol factor 67K
  • NADP
  • cytochrome b558
  • CYBB protein, human
  • NADPH Oxidase 2
  • NADPH Oxidases
  • CYBA protein, human
  • neutrophil cytosolic factor 1
  • NADPH Dehydrogenase
  • Oxygen