ADI1 (acireductone dioxygenase 1) is a metal-dependent dioxygenase that catalyzes two distinct reactions depending on its iron or nickel cofactor. The iron-containing form (Fe-ARD) produces formate and 2-keto-4-methylthiobutyrate, functioning as a key enzyme in the methionine salvage pathway 1. ADI1 expression is tightly regulated by cellular iron levels through proteasome-mediated degradation, with the iron chaperone PCBP1 playing a critical role in its expression 2. Beyond its metabolic function, ADI1 exhibits tumor-suppressive activities. In prostate cancer, ADI1 is downregulated, and its reintroduction induces apoptosis, though this effect does not require its catalytic metal-binding activity 3. In hepatocellular carcinoma, ADI1 reduces tumor growth by enhancing the methionine salvage pathway, which increases S-adenosylmethionine levels and alters genome-wide promoter methylation patterns, suppressing expression of growth-promoting genes like caveolin-1 4. ADI1 also suppresses cell migration via MMP14 inhibition and supports hepatitis C virus entry in non-permissive cells 5. In Drosophila, ADI1 is essential for normal fecundity through methionine metabolism regulation 6. These findings establish ADI1 as a multifunctional enzyme integrating metabolic and tumor-suppressive roles.