InterPro domain: IPR011048

Cytochrome cd1 (cyt cd1) nitrite reductase is a dimeric enzyme of the bacterial periplasm that plays a key role in denitrification, the respiratory reduction of nitrite to nitric oxide in the nitrogen cycle. Each subunit of the cyt cd1 dimer contains one cytochrome c and one d1 haem group [ 1 ]. The active site contains a specialised d1 haem, where the nitrite substrate is bound and reduced. This d1 haem is bound in an 8-bladed beta-propeller, which is also found in some members of the WD40 repeat-containing proteins ( IPR001680 ). This superfamily represents the d1 heme binding domain.

1. Structure and kinetic properties of Paracoccus pantotrophus cytochrome cd1 nitrite reductase with the d1 heme active site ligand tyrosine 25 replaced by serine. J. Biol. Chem. 278, 11773-81