detection by mass spectrometry of highly increased amount of S- sulfonated transthyretin in serum from a patient with molybdenum cofactor deficiency

Abstract

Serum transthyretin has several isoforms, most of which are caused by disulfide linkage with cysteine residue at position 10. We found an ion peak 80 D larger than unmodified transthyretin by electrospray ionization mass spectrometry and assigned it toS-sulfonated transthyretin. The peak height was “2% of total transthyretin in control sera from more than 200 individuals including infants. Transthyretin from a patient with molybdenum cofactor deficiency was analyzed, and the peak was prominent, higher than 85% of total transthyretin. In patients with this disease, the presence of elevated levels of sulfite leads to the formation ofS-sulfonated cysteine. The peak can be used as a diagnostic marker for molybdenum cofactor deficiency, although more sera from patients with this disease should be tested.© International Pediatrics Research Foundation, Inc. 2000. All Rights Reserved.