K4519 Sigma


lyophilized powder

Synonym: KerA, Keratinase from Bacillus licheniformis, Keratinolytic protease


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

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