The Enzymatic Synthesis of Protected Valine-5 Angiotensin II Amide-1

An example of the use of proteolytic enzymes to facilitate the peptide synthesis by fragment condensation is provided for the preparation of protected valine-5 angiotensin II amide-1 using t-butoxycarbonylpeptides as a carboxyl component and a peptide ethyl ester as an amine component. The proteolytic enzymes used are papain, nagarse (subtilisin BPN′) and microbial metalloenzyme isolated from St. caespitosus. Papain-catalyzed condensation reaction afforded the corresponding oligopeptide in the ester form, whereas nagarse and microbial metalloenzyme-catalyzed condensation reactions afforded the products in the carboxyl free form. Assignment of the product was made on the basis of a comparison of physical properties with those of the peptide prepared by the solution method.