Role of carbohydrate in rat plasma thiostatin: Deglycosylation destroys cysteine proteinase inhibition activity

Abstract Rat plasma thiostatin, a 68kDa glycoprotein cysteine proteinase inhibitor, was chemically deglycosylated with trifluoromethanesulfonic acid. Both native and deglycosylated species were characterized with regard to amino acid and carbohydrate composition, homogeneity by SDS-PAGE, immunoreactivity by Western blot, and cysteine proteinase inhibitor activity. Deglycosylation of thiostatin did not alter the integrity of the protein backbone nor change the immunologic recognition of the molecule by polyclonal rabbit anti-rat thiostatin. However, deglycosylation did destroy cysteine proteinase inhibitor activity activity as measured against papain.