4.2.1.117 | physiological function |
the two genes acnD and prpF, encoding 2-methylcitrate dehydratase (AcnD, EC 4.2.1.117) and 2-methyl-aconitate isomerase (SoPrpF, EC 5.3.3.-) from Shewanella oneidensis together can replace gene prpD from Salmonella enterica, which encodes 2-methylcitrate dehydratase, PrpD /EC 4.2.1.79. SoAcnD and SePrpD synthesize different methylaconitate isomers. The SoPrpF protein isomerizes the product of the AcnD reaction into the PrpD product (2-MCA), known substrate of the housekeeping aconitase. It is likely that 4-methylaconitate is the product of the AcnD enzyme. PrpF (SoPrpF) protein isomerizes the product of the SoAcnD dehydratase (putatively 4-methyl-cis-aconitate (4-MCA)) to 2-methyl-cis-aconitate (2-MCA). Thus,the role of SoPrpF in the 2-methylcitrate cycle (2-MCC) is to change the stereochemistry of the SoAcnD reaction product. AcnD and PrpF activities are necessary and sufficient to compensate for the lack of PrpD during growth with propionate of the strain of Salmonella enterica. 2-Methylcitrate is dehydrated by AcnD to 4-methyl-cis-aconitate, which is then isomerized to 2-methyl-cis-aconitate by PrpF, and rehydrated to 2-methylisocitrate by aconitases A and B |
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