The synthesis of methionine by enzymic transmethylation: VI. Studies of the homogeneity, shape properties and monomer functionality of thetin-homocysteine methylpherase

Abstract

It has been demonstrated, by means of moving partition cell ultracentrifugation, that the sedimentation coefficients of the enzymic activity of thetin-homocysteine methylpherase and of the total protein present in the system are the same over a wide range of degrees of polymerization. This observation is believed to be a highly sensitive criterion of homogeneity, and one which should be applicable to a number of other protein systems which may be studied at different degrees of aggregation. Hydrodynamic studies of monomer and polymer preparations have shown that the shape of each of the components of THMenz polymer preparations is very close to that of the monomer. Direct observation by electron microscopy has confirmed this result. In accordance with this concept, it has been shown by application of the Stockmayer statistical theory of polymerization to the THMenz system that there are three functional groups on each monomer residue which can form intermolecular disulfide bonds in the polymerization reaction and that therefore the polymer molecules are three dimensional aggregates as opposed to linear ones.