CDO1 (cysteine dioxygenase, type I) is a 200 amino acid protein that belongs to the cysteine dioxygenase family and is involved in organosulfur biosynthesis. Existing as a monomer and expressed at high levels in liver and placenta and at lower levels in brain, pancreas and heart, CDO1 functions as a dioxygenase that uses iron and zinc as cofactors to catalyze the conversion of L-cysteine and oxygen to 3-sulfinoalanine. Via its catalytic activity, CDO1 is involved in pyruvate-, sulfate- and taurine-related metabolic pathways and is a crucial regulator of cysteine concentrations within the cell. Human CDO1 shares 94% amino acid identity with its rat counterpart, suggesting a conserved role between species. The gene encoding CDO1 maps to human chromosome 5, which contains 181 million base pairs and comprises nearly 6% of the human genome. Deletion of the p arm of chromosome 5 leads to Cri du chat syndrome, while deletion of the q arm or of chromosome 5 altogether is common in therapy-related acute myelogenous leukemias and myelodysplastic syndrome.PathwayOrganosulfur biosynthesis; taurine biosynthesis; hypotaurine from L-cysteine: step 1 2.