Plastein, a Mixture of Higher-molecular Polypeptides Synthesized by Proteolytic Enzymes.

Abstract

The former idea of the low molecular wt. of plasteins (less than 1000) does not agree with the more recent findings of Virtanen''s laboratory. The parallel viscosmetric detns. with plastein prepns. and with polypeptide fractions formed in the hydrolysis of zein as well as the cryoscopic detn. using a non-polar solvent (lactam of 4-aminocyclohexane carboxylic acid) support the concept that the avg. molecular wt. of plasteins is several thousands. The diffusion expts. also lead to similar results. Accordingly, the plasteins must be regarded as open polypeptides whose alpha-amino N results from the end groups. Thus pepsin causes both the hydrolysis and synthesis of polypeptides.