Characterization and optimization of two-chain folding pathways of insulin via native chain assembly

Kenta Arai, Toshiki Takei, Reina Shinozaki, Masato Noguchi, Shouta Fujisawa, Hidekazu Katayama, Luis Moroder, Setsuko Ando, Masaki Okumura, Kenji Inaba, Hironobu Hojo, Michio Iwaoka

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


Until recently the total synthesis of insulin, with its characteristic heterodimeric structure crosslinked by two interchain and one intrachain disulfide (SS) bridge, remained largely an unsolved challenge. By optimizing the synthesis and directed disulfide crosslinking of the two chains, and by applying biomimetic monocomponent proinsulin approaches, efficient insulin syntheses have been realized. Here we report the optimization and characterisation of an alternative strategy, oxidative native chain assembly. In this method unprotected A- and B-chains assemble oxidatively under thermodynamic control to afford bovine pancreatic insulin in 39% yield. Folding is found to proceed predominantly via structured 1SS* and 2SS* intermediates with a common interchain CysA20‒CysB19 disulfide. These results suggest that native chain assembly, long considered inefficient, may represent a reasonable strategy to access insulin variants. This is supported by the synthesis of human insulin and human type-II relaxin in yields of up to 49 and 47%, respectively, although the application to human insulin ValA16 variant is unsuccessful.

Original languageEnglish
Article number26
JournalCommunications Chemistry
Issue number1
Publication statusPublished - 2018 Dec 1


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