K4519 Sigma


lyophilized powder

Synonym: KerA, Keratinase from Bacillus licheniformis, Keratinolytic protease



Related Categories 3.4.x.x Peptidases, 3.x.x.x Hydrolases, Biochemicals and Reagents, Enzyme Class Index, Enzymes, Inhibitors, and Substrates,
recombinant   expressed in E. coli BL21
form   lyophilized powder
mol wt   mol wt ~39 kDa
pH-range   5.5 - 12.5 (optimum activity is seen at pH 12.5)
pI    8.73
storage temp.   −20°C


Other Notes

This enzyme contains a C-terminus 6-Histidine tag.

Preparation Note

The enzyme can be solubilized at 0.5-1.0 mg/mL in either sterile water or phosphate buffer. The best activity is seen with freshly prepared solutions. However, single-use aliquots of Keratinase solutions can be stored at -20° C.


Keratin. Keratinases have also been used for the degradation of prion and prion-like proteins.

Unit Definition

One unit of enzyme is able to hydrolyze casein resulting in an absorbance value as the Folin-Ciocalteau reagent equivalent to 1 umole (181μg) of tyrosine per minute at pH 7.5 at 37 °C.


Keratinase was used for enzymatic treatment of elementary body (EB), GAG molecules, and cells in the study of the role glycosaminoglycans (GAGs) in the invasion of host cells by Chlamydia pneumoniae strains.1

Biochem/physiol Actions

Keratinase is a particular class of extracellular proteolytic inducible enzyme with the capability of degrading insoluble keratin substrates. 2,3 It is important for hydrolyzing hair, feather, and collagen in sewage system during waste water treatment. It is also useful in food industry, animal feed preparation etc.4 Insoluble feather keratin from poultry industry may be converted by enzymatic hydrolysis to glues, feedstuffs, fertilizers, films or used for the production of rare amino acids serine, cysteine and proline.2

General description

Keratinase is a non-specific serine protease that cleaves non-terminal peptide bonds. This enzyme is active between 37°- 70°C. The highest activity is typically seen at 70°C.

Physical properties

Keratinase is activated by 0.10% SDS, 1.0% CTAB, and EDTA. Keratinase is partially inhibited by Tween®20, DMSO, isopropanol, methanol, and ethanol.

Legal Information

TWEEN is a registered trademark of Croda International PLC

Price and Availability

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recombinant, expressed in E. coli, ≥140 units/mg protein, buffered aqueous solution

Keratin from human epidermis

aqueous solution

Safety & Documentation

Safety Information

GHS07  GHS07
Signal word 
Hazard statements 
Precautionary statements 
WGK Germany 


Certificate of Analysis

Certificate of Origin

Protocols & Articles

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Peer-Reviewed Papers


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1. Comparative studies of glycosaminoglycan involvement in Chlamydia pneumoniae and C. trachomatis invasion of host cells. Beswick EJ, Travelstead A, and Cooper MD J. Infect. Dis. 187(8), 1291-300, (2003)


2. Bacterial Keratinases: Useful Enzymes for Bioprocessing Agroindustrial Wastes and Beyond. Brandelli A Food Bioprocess Tech. 1(2), 105-116, (2008)

3. Keratinase production and keratin degradation by a mutant strain of Bacillus subtilis. Cai CG, Lou BG, and Zheng XD J. Zhejiang Univ. Sci. B 9(1), 60-7, (2008)


4. Keratinolytic activity from the broth of a feather-degrading thermophillic Streptomyces thermoviolaceus strain SD8. Chitte RR, Nalawade VK, Dey S. Lett. Appl. Microbiol. 28, 131-136, (1999)

Characterization of a proetolytic enzyme derived from a Bacillus strain that effectively degrades prion proteins. Yoshioka, M. et al. J. Appl. Microbiol. 102, 509-515, (2007)


An investigation into keratinolytic enzymes to enhance ungual drug delivery, Mohorcic, M. et al. Int. J. Pharm. 332, 196-201, (2007)


Decomposition of extremely hard-to-degrade animal proteins by thermophilic bacteria. Suzuki, Y. et al. J. Biosci. Bioeng. 102, 73-81, (2006)


Degradation of PrPSc by keratinolytic protease from Nocardiopsis sp. TOA-1. Mitsuiki, S. et al. Biosci. Biotechnol. Biochem. 70, 1246-1248, (2006)


Bacterial keratinases: useful enzymes for bioprocessing agroindustrial wastes and beyond. Brandelli, A. Food Bioprocess Tech. 1, 105-116, (2008)

Screening for a new Streptomyces strain capable of efficient keratin degradation. Chao, Y. P. et al. J. Environ. Sci. Health 19, 1125-28, (2007)

In vitro degradation of porcine skin epidermis by a fungal keratinase of Doratomyces microsporus. Enzyme Microb. Technol. 36, 450-460, (2005)

Expression of the Bacillus licheniformis PWD-1 keratinase gene in B. Subtilis. Lin, X. et al. J. Ind. Microbiol. 19, 134-138, (1997)

Purification and Characterization of a Keratinase from a Feather-Degrading Bacillus licheniformis Strain. Lin X, Lee CG, Casale ES, et al. Appl. Environ. Microbiol. 58(10), 3271-5, (1992)


Similarities and specificities of fungal keartinolytic proteases: comparison of keratinases of Paecilomyces marquandii and Doratomyces microspores to some known proteases. Gradisar, H. et al. Appl. Environ. Microbiol. 71, 3420-3426, (2005)


Similarities and specificities of fungal keartinolytic proteases: comparison of keratinases of Paecilomyces marquandii and Doratomyces microspores to some known proteases. Gradisar, H. et al. Appl. Environ. Microbiol. 71, 3420-3426, (2005)


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