Papain-Catalyzed Synthesis of Polyglutamate Containing a Nylon Monomer Unit

Abstract

Abstract:Peptides have the potential to serve as an alternative for petroleum-based polymers to support a sustainable society. However, they lack thermoplasticity, owing to their strong intermolecular interactions. In contrast, nylon is famous for its thermoplasticity and chemical resistance. Here, we synthesized peptides containing a nylon unit to modify their thermal properties by using papain-catalyzed chemoenzymatic polymerization. We used L-glutamic acid alkyl ester as the amino acid monomer and nylon 1, 3, 4, and 6 alkyl esters as the nylon unit. Papain catalyzed the copolymerization of glutamic acid with nylon 3, 4, and 6 alkyl esters, whereas the nylon 1 unit could not be copolymerized. Other proteases used in this study, namely, bromelain, proteinase K, and Candida antarctica lipase (CALB), were not able to copolymerize with any nylon units. The broad substrate specificity of papain enabled the copolymerization of L-glutamic acid with a nylon unit. The peptides with nylon units demonstrated different thermal profiles from that of oligo(L-glutamic acid). Therefore, the resultant peptides with various nylon units are expected to form fewer intermolecular hydrogen bonds, thus altering their thermal properties. This finding is expected to broaden the applications of peptide materials and chemoenzymatic polymerization.

Periodic introduction of aromatic units in polypeptides via chemoenzymatic polymerization to yield specific secondary structures with high thermal stability

“…The introduction of unnatural structures into a polypeptide backbone allows polypeptide materials to obtain novel functionalities and improved physical properties. In our previous study, we successfully introduced nylon units, a synthetic amino acid for commercial polyamides, into polypeptides via chemoenzymatic polymerization of leucine and nylon ethyl esters using papain [21,22]. A melting point could be detected for the polypeptide with a random sequence of leucine and nylon units, whereas no such transition could be detected for polyleucine below its decomposition temperature.…”

Chemoenzymatic Synthesis of Polypeptides for Use as Functional and Structural Materials

“…Methyl, [49] ethyl [45] Proteinase I, [49] proteinase K (5-9) [45] l-Glutamic acid Ethyl [45,46,49,59,62,[71][72][73] Proteinase I, [49] papain (6-9.5), [59,62,[71][72][73] α-chymotrypsin (5-12), [59] proteinase K (5-9), [45] bromelain (5-9), [46,59] protease SG (6-11) [59] l-Aspartic acid Ethyl [49] Proteinase I [49] l-Tryptophan…”

“…Methyl [79] Alkaline d-peptidase (2-4) [79] Aib b) Ethyl [123] Papain (4-5) [123] 3-Aminopropionic acid Methyl, [73,124] ethyl [73,124] Papain (6-9) [73,124] 4-Aminobutyric acid Methyl, [73,124] ethyl [73,124] Papain (5-9) [73,124] 6-Aminohexanoic acid Methyl [73,124] Papain (6-9) [73,124] a) Values in parentheses show the range of average degree of polymerization (DP) obtained using the proteases; b) Polymerization was conducted using a tripeptide ester containing an Aib unit.…”

“…[73,124] When the diethyl l-glutamate was enzymatically copolymerized with various nylon monomers, including ethyl 3-aminopropionate, ethyl 4-aminobutyrate, and methyl 6-aminohexanoate, polypeptides containing nylon units were obtained. [73] However, a large excess (ninefold) of nylon monomers relative to diethyl l-glutamate was required. The incorporation of nylon units was achieved only…”

“…Polypeptides that assume unnatural structures: A) star-shaped polypeptides, [44,70] B) telechelic polypeptides, [55,117] C) polypeptides containing Aib as an unnatural amino acid, [123] and D) polypeptides containing nylon units. [73,124] www.advancedsciencenews.com www.mbs-journal.de with papain, although several proteases, such as bromelain, proteinase K, and lipase, were tested. This is probably because of the relatively broad substrate specificity of papain.…”