Enzyme Activity Measurement of Sulfite Oxidase Using Spectrophotometric Assays

Creative Enzymes supports scientists and researchers from all around the world with well-controlled testing services. The advanced instruments and professional experts make enzyme activity assays a convenient and efficient process. We have developed assay methods suitable for different oxidoreductases. As for sulfite oxidase, we provide reliable custom assays to address any concerns with the enzyme activity determination.

Sulfite oxidase (EC 1.8.3.1) is a member of the molybdenum oxotransferase super-family and catalyzes the oxidation of sulfite to sulfate, using molybdenum as a cofactor. This enzyme locates in mitochondria and can be found in all eukaryotes. Upon oxidation of sulfite, Mo(VI) is reduced to Mo(IV) by two electrons. The electrons are subsequently transferred to the heme Fe(III) in the cytochrome b5 domain, followed by electron transfer to cytochrome c. The electrons later enter the electron transport chain, generating ATP through oxidative phosphorylation.

The reaction catalyzed by sulfite oxidase is vital for humans. It is the final step in the degradation of sulfur-containing amino acids such as cysteine and methionine as well as the sulfate excretion. Once the enzyme is deficient, it will lead to metabolic disorders of xanthine and sulfite. Sulfocysteinuria is a rare autosomal recessive condition because of the deficiency of sulfite oxidase. The affected patients usually have neurological abnormalities, such as multicystic leukoencephalopathy with brain atrophy, seizures, generalised dystonia, and choreoathetosis. Severe conditions may even cause minimal development of language and death at the age of 1 or 2 years. Studies have shown that the Arg-160 residue is conserved among all sulfite oxidases sequenced to date, and its mutation will cause a sharp decrease in activity. Nowadays, the detection of this enzyme is one of the required physical examinations for the newborn. To better understand this disease and develop efficient means for diagnosis, a number of research has been carried out to obtain detailed structural information and establish accurate assay approaches during pregnancy. Given the clinical significance of sulfite oxidase, Creative Enzymes actively provide high-quality enzyme activity assays to support your research.

Figure: The crystal structure of recombinant chicken sulfite oxidase at the resting state.
Reference: Karakas E et al. J Biol Chem. 2005 280(39):33506-33515

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