Chemoenzymatic synthesis of polypeptides consisting of periodic di- and tri-peptide motifs similar to elastin

Proline and valine exist in repetitive motifs in various structural proteins and play an important role in their physiological functions. Herein, we synthesized polypeptides that consist of di- and tri-peptide motifs containing proline and valine via chemoenzymatic polymerization. Di- and tri-peptide ethyl esters (ValGly-OEt, GlyProGly-OEt, and ValProGly-OEt) could be polymerized by papain, whereas proline and valine ethyl esters (Pro-OEt, Val-OEt) were inactive in chemoenzymatic polymerization because of their poor affinity for papain. The copolymer of ValProGly-OEt and ValGly-OEt being poly(ValProGly-co-ValGly), which is composed of a repetitive sequence of elastin, exhibited a temperature-dependent structural transition similar to tropoelastin. The post-polycondensation product of poly(ValProGly-co-ValGly) showed higher molecular weight and elastin-like thermal behaviors.