When Yeast lysyl-tRNA-ligase is extracted in the presence of protease inhibitor (PMSF) a homogeneous species of enzyme is obtained, the subunits of which have a mass of 70 000 daltons. Endogenous degradation produces lighter active species of the enzyme, dimers with subunits in the range 50 000–60 000 daltons. Partial trypsinolysis mimics this degradation, which is therefore thought to occur through proteolysis.
