Overview of Oxygen Activating Heme Enzymes

Most well-studied peroxidases are designed to oxidize small aromatic molecules, with the exception of cytochrome c peroxidase. It generally is thought that such aromatic molecules bind near the heme edge where an electron can transfer directly to the heme edge (44), which is supported by both crystal structures (45, 46) and NMR studies (47). However, recent work suggests that some physiologically important substrates may utilize other sites on the enzyme surface (48, 49). 

Although the heme-binding N-terminal half of NOS bears no sequence similarity to P450s, the spectral properties of the Fe +-CO complex with the characteristic 450 nm Soret maximum (72-74) clearly places NOS in the category of P450-like thiolate enzymes. The architecture of NOS also is strikingly similar to cytochrome P450BM-3 (75) 

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