| Type: | Family | Name: | Acireductone dioxygenase ARD family |
| Description: | The two acireductone dioxygenase enzymes (ARD and ARD', previously known as E-2 and E-2') from Klebsiella pneumoniaeshare the same amino acid sequence , but bind different metal ions: ARD binds Ni2+, ARD' binds Fe2+ []. ARD and ARD' can be experimentally interconverted by removal of the bound metal ion and reconstitution withthe appropriate metal ion. The two enzymes share the same substrate, 1,2-dihydroxy-3-keto-5-(methylthio)pentene, but yield different products. ARD' yields the alpha-keto precursor of methionine (and formate), thus forming part of theubiquitous methionine salvage pathway that converts 5'-methylthioadenosine (MTA) to methionine. This pathway is responsible for the tight control of the concentration of MTA, which is a powerful inhibitor of polyamine biosynthesis andtransmethylation reactions []. ARD yields methylthiopropanoate, carbon monoxide and formate, and thus prevents theconversion of MTA to methionine. The role of the ARD catalysed reaction is unclear: methylthiopropanoate is cytotoxic, and carbon monoxide can activate guanylyl cyclase, leading to increased intracellular cGMP levels [, ]. Eukaryotic aci-reductone dioxygenase (ARD), also known as 1,2-dihydroxy-3-keto-5-methylthiopentene dioxygenase, acts in the methionine salvage pathway []. Several homologous ARD genes have been identified in plants []. | Short Name: | ARD |
