Iron Based
There are several types of iron based enzymes. Cytochrome cd1, or Pseudomonas cytochrome oxidase contains two c and two d type hemes with two polypeptide chains. Different forms of this reductase catalyze the formation of nitric oxide or nitrous oxide. A version of this compound was originally called . It was initially considered an oxidase. It catalyzes the reduction of NO2- to NO. This tetraheme enzyme has two subunits, each containing a c-type and a d-type heme. The reduced d hemes bind nitrite and convert it to product.
Cytochrome c nitrite reductase (ccNIR) is a multiheme enzyme that converts nitrite to ammonia on each active site. The active site iron is bound to a protoporphyrin IX ring that is covalently linked to the enzyme's proteins.
Read more about this topic: Nitrite Reductase
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