Development of a keratinase activity assay using recombinant chicken feather keratin substrates

Hyeon Su Jin, Seon Yeong Park, Kyungmin Kim, Yong Jik Lee, Gae Won Nam, Nam Joo Kang, Dong Woo Lee

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Poultry feathers consist mainly of the protein keratin, which is rich in β-pleated sheets and consequently resistant to proteolysis. Although many keratinases have been identified, the reasons for their substrate specificity towards β-keratin remain unclear due to difficulties in preparing a soluble feather keratin substrate for use in activity assays. In the present study, we overexpressed Gallus gallus chromosomes 2 and 27 β-keratin-encoding genes in Escherichia coli, purified denatured recombinant proteins by Ni2+ affinity chromatography, and refolded by stepwise dialysis to yield soluble keratins. To assess the keratinolytic activity, we compared the proteolytic activity of crude extracts from the feather-degrading bacterium Fervidobacterium islandicum AW-1 with proteinase K, trypsin, and papain using purified recombinant keratin and casein as substrates. All tested proteases showed strong proteolytic activities for casein, whereas only F. islandicum AW-1 crude extracts and proteinase K exhibited pronounced keratinolytic activity for the recombinant keratin. Moreover, LC-MS/MS analysis of keratin hydrolysates allowed us to predict the P1 sites of keratinolytic enzymes in the F. islandicum AW-1 extracts, thereby qualifying and quantifying the extent of keratinolysis. The soluble keratin-based assay has clear therapeutic and industrial potential for the development of a high-throughput screening system for proteases hydrolyzing disease-related protein aggregates, as well as mechanically resilient keratin-based polymers.

Original languageEnglish
Article numbere0172712
JournalPloS one
Issue number2
Publication statusPublished - 2017 Feb

Bibliographical note

Publisher Copyright:
© 2017 Jin et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

All Science Journal Classification (ASJC) codes

  • General


Dive into the research topics of 'Development of a keratinase activity assay using recombinant chicken feather keratin substrates'. Together they form a unique fingerprint.

Cite this