Physical and chemical characterization of macroglobulin from marine turtle eggwhite.

Macroglobulin was purified from the eggwhite of the marine turtle (Caretta caretta Linn.) by gel filtration through Sephadex G-200 and Sepharose 4B. It was characterized by physical techniques including sedimentation velocity, diffusion and viscosity. Its molecular weight (Mr) was determined as 724,000 with four subunits of equal molecular weight. A large amount of water was hydrodynamically associated with the macroglobulin. It inhibited the activities of trypsin and papain and did not cross-react with human alpha 2-macroglobulin. Its amino acid composition was similar to that of human alpha 2-macroglobulin. Results suggest that turtle eggwhite macroglobulin is a homologous but distinct protein from human alpha 2-macroglobulin.