β-Hydroxyaspartic acid in vitamin K-dependent plasma proteins from scorbutic and warfarin-treated guinea pigs

Abstract

β-Hydroxyaspartic acid is a rare amino acid, present in all vitamin K-dependent plasma proteins except prothrombin, and is formed by a post-translational hydroxylation of aspartic acid. We have now investigated whether this hydroxylation, like that of proline in collagen, is vitamin C-dependent. The vitamin K-dependent plasma proteins were isolated from normal and scorbutic guinea pig plasma by barium citrate adsorption and the β-hydroxyaspartic acid content was determined. Compared with normal animals, scorbutic animals showed no significant reduction of β-hydroxyaspartic acid content. In warfarin-treated animals there was a decreased content of both β-hydroxyaspartic acid and γ-carboxyglutamic acid in the barium citrate adsorbed fraction. It was concluded that the post-translational hydroxylation of aspartic acid is unlikely to be vitamin C-dependent.