cytochrome b5 reductase 4 (flavohemoprotein b5/b5R, b5+b5R, cb5/cb5R, N-terminal cytochrome b5 & cytochrome b5 oxidoreductase domain-containing protein, CYB5R4, NCB5OR)

Function

• NADH-cytochrome b5 reductase
• role in endolasmic reticulum stress response pathway
• role in protecting pancreatic beta-cells against oxidant stress, possibly by protecting the cell from excess buildup of reactive oxygen species
• reduces a variety of substrates in vitro, including
  • cytochrome c
  • ferricyanide
  • methemoglobin

NADH + 2 ferricytochrome b5 <--> NAD+ + 2 ferrocytochrome b5

Cofactor: FAD

Kinetic parameters:

• KM=25 mM for O2
• Redox potential: E(0) is -108 mV

Structure

• belongs to the flavoprotein pyridine nucleotide cytochrome reductase family
• contains 1 CS domain
• contains 1 cytochrome b5 heme-binding domain

Compartment

• endoplasmic reticulum, (soluble protein)

Expression

widely expressed

Polymorphism

• variants Arg-187 & Arg-223 do not influence the pathogenesis of non-autoimmune diabetes

More general terms

• NADH cytochrome b5 reductase; NADH-methemoglobin reductase

Database

• OMIM: https://mirror.omim.org/entry/608343
• UniProt: http://www.uniprot.org/uniprot/Q7L1T6.html