| Type: | Domain | Name: | Haem oxygenase-like, multi-helical |
| Description: | This entry represents a multi-helical structural domain consisting of two structural repeats (duplication) of a 3-helical motif. This domain can be found in both eukaryotic and prokaryotic haem oxygenases [, ], in TENA/THI-4 proteins that lack the haem-binding site [], and in coenzyme PQQ (pyrrolo-quinoline-quinone) biosynthesis protein C (PqqC) [].Haem oxygenase () (HO) is the microsomal enzyme that, in animals, carries out the oxidation of haem, cleaving the haem ring at the alpha-methene bridge to form biliverdin and carbon monoxide. Biliverdin is subsequently converted to bilirubin by biliverdin reductase. In mammals there are three isozymes of haem oxygenase: HO-1 to HO-3. The first two isozymes differ in their tissue expression and their inducibility: HO-1 is highly inducible by its substrate haem and by various non-haem substances, while HO-2 is non-inducible. Haem oxygenase is also present in certain bacteria, where it is involved in the acquisition of iron from the host haem.The THI-4 protein is involved in thiamine biosynthesis, while TENA is one of a number of proteins that enhance the expression of extracellular enzymes, such as alkaline protease, neutral protease and levansucrase.Coenzyme PQQ (pyrrolo-quinoline-quinone) biosynthesis protein C (PqqC; ) is required for the synthesis of PQQ, where PQQ is a prosthetic group found in several bacterial enzymes, including methanol dehydrogenase of methylotrophs and the glucose dehydrogenase of a number of bacteria. | Short Name: | Haem_Oase-like_multi-hlx |
