Catalyzes 2 different reactions between oxygen and the acireductone 1,2-dihydroxy-3-keto-5-methylthiopentene (DHK-MTPene) depending upon the metal bound in the active site (By similarity). Fe-containing acireductone dioxygenase (Fe-ARD) produces formate and 2-keto-4-methylthiobutyrate (KMTB), the alpha-ketoacid precursor of methionine in the methionine recycle pathway (PubMed:15938715). Ni-containing acireductone dioxygenase (Ni-ARD) produces methylthiopropionate, carbon monoxide and formate, and does not lie on the methionine recycle pathway (By similarity). Also down-regulates cell migration mediated by MMP14 (PubMed:14718544). Necessary for hepatitis C virus replication in an otherwise non-permissive cell line (PubMed:11602742). 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + O2 = 4-methylsulfanyl-2-oxobutanoate + formate + 2 H(+) 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + O2 = 3-(methylsulfanyl)propanoate + CO + formate + 2 H(+) Binds either 1 Fe or Ni cation per monomer. Iron-binding promotes an acireductone dioxygenase reaction producing 2-keto-4-methylthiobutyrate, while nickel-binding promotes an acireductone dioxygenase reaction producing 3-(methylsulfanyl)propanoate. Amino-acid biosynthesis; L-methionine biosynthesis via salvage pathway; L-methionine from S-methyl-5-thio-alpha-D-ribose 1-phosphate: step 5/6. Monomer (By similarity). Interacts with MMP14. Localizes to the plasma membrane when complexed to MMP14. Detected in heart, colon, lung, stomach, brain, spleen, liver, skeletal muscle and kidney. Belongs to the acireductone dioxygenase (ARD) family. Truncated N-terminus. Extended N-terminus. Extended N-terminus.