Sulfite oxidase is the last enzyme in the pathway for degradation of sulfur-containing amino acids. Cofactor for sulfite oxidase is:

Sulfite oxidase (SO) catalyzes the oxidation of sulfite to sulfate, using the heme-containing protein, cytochrome c, as electron acceptor. It is the last enzyme in the pathway for degradation of sulfur-containing amino acids. Molybdenum acts as cofactor for sulfite oxidase. Autosomal recessive disorders of sulfur metabolism, manifest clinically during the neonatal period by seizures, axial hypotonia, reduced level of responsivity, and spasms with opisthotonus. Ref: Biochemistry By Reginald H. Garrett, Charles M. Grisham, 2012, Page 422.