Microheterogeneity of Human Antithrombin III

Abstract

Antithrombin purified from normal human plasma was separated into 2 fractions by isoelectric focusing in a pH 4-6 gradient. These fractions were homogeneous by polyacrylamide gel electrophoresis, had similar amino acid composition and the same specific activity. Both of them cross reacted with antiserum against antithrombin. The contained different amounts of sialic acid and aminosugars. After neuraminidase treatment only a single, homogeneous peak was found by isoelectric focusing.sbd.with unchanged antithrombin activity.sbd.suggesting that the microheterogeneity is due to a difference in glycosylation.