CRAYFISH ALPHA-MACROGLOBULIN AS A SUBSTRATE FOR TRANSGLUTAMINASES

Two fluorescent transglutaminase substrates, dansylcadaverine and a dansylated peptide (dansyl-Pro-Gly-Gly-Gln-Gln-Ile-Val), were used to detect glutamine and lysine, respectively, as putative transglutaminase cross-linking residues on purified crayfish alpha-macroglobulin. Endogenous transglutaminase activities, present in the homogenates of crayfish haemocytes and crayfish abdominal muscle, incorporated the dansylated peptide into crayfish alpha-macroglobulin, while guinea-pig liver transglutaminase incorporated both dansylcadaverine and the dansylated peptide. Methylamine treatment induces a conformational change in the crayfish alpha-macroglobulin molecule that also affects its properties as a transglutaminase substrate. None of the dansylated probes were incorporated by the different transglutaminases into methylamine-treated crayfish alpha-macroglobulin.