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Front. Catal.
Sec. Biocatalysis
Volume 3 - 2023 | doi: 10.3389/fctls.2023.1275281

The Chemoenzymatic Synthesis of Glycan-Terminated Oligo(Leu)x

 Sarah P. Black1 Melinda Liu2  Cesar Castillo1 Wynne Coradeli1 Filbert Totsingan1 Cody B. Edson1 Sagar D. Khare2  Richard A. Gross1*
  • 1Rensselaer Polytechnic Institute, United States
  • 2Rutgers University, Newark, United States

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Glycopeptides contain carbohydrate moieties (glycans) covalently attached to the side chain and/or terminal peptide units. Since glycans are present on cell surfaces, these constructs can potentially address a wide array of therapeutic functions. To overcome the deficiencies associated with current synthetic routes to glycopeptides, such as costly processes and toxic reagents, this work aimed to develop versatile environmentally friendly protease-catalyzed peptide synthetic (PCPS) routes to peptides decorated with a glycan at their N-terminus. 'Grafters' were first synthesized that consist of a glycan conjugated directly, or through a spacer, to the amine group of L-Phe-ethyl ester (Phe-OEt). The role of Phe-OEt is to increase the conjugate's recognition by the protease (papain) catalytic active site. A series of grafters were synthesized with variation of the glycan structure, linkage-chemistry, and presence of an oligo(ethylene glycol) 'spacer' of varied length between the glycan and Phe-OEt moiety. High grafter efficiency will result by the successful acceptance of the grafter at the enzymes S1/S2 subsites, formation of an acyl-enzyme complex and subsequent conversion to glycan-terminated-oligo(Leu)x (x ≥ 1), as opposed to construction of non-glycan Nterminated oligo(Leu)x. While glycan-Phe-OEt grafters without a spacer between the glycan and Phe-OEt resulted in low grafter efficiency (8.3 ± 2.0%), insertion of a short oligo(ethylene glycol) spacer between the glycan and Phe-OEt moieties (glycan-PEGn-Phe-OEt, n ≥ 3) increased the grafter efficiency by 3-fold to 24.5 ± 1.8%. In addition, computational modeling was performed using Rosetta software provided insights on a molecular level of how grafter efficiency is influenced by the PEG spacer length.

Keywords: Glycan-terminated, Oligopeptide, protease catalysis, Papain, computational modeling

Received: 09 Aug 2023; Accepted: 22 Sep 2023.

Copyright: © 2023 Black, Liu, Castillo, Coradeli, Totsingan, Edson, Khare and Gross. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Richard A. Gross, Rensselaer Polytechnic Institute, Troy, United States