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Keratinases are proteolytic enzymes in nature. They were classified as proteinases of unknown mechanism as recommended by the Nomenculture Committee on the International Union of Biochemistry (1978) with EC number 3.4.99 (Owen et al., 1983). Recently, some researchers defined keratinase as a serine protease due to its 97% sequence homology with alkaline protease, and it is also inhibited by the same inhibitor that inhibits serine protease (Wang et al., 1995; Taha et al., 1998 and Bressollier et a1., 1999).

Keratinases are produced only in the presence of keratin-containing substrate. They mainly attack the disulfide (-S-S-) bond of the keratin substrate (Bockel et al., 1995). Keratinase production in various microorganisms was reported on by a number of researchers. It was found that keratinase in fungi, Streptomyces and bacteria were produced in nearly at alkaline pH and almost thermophilic temperatures. These enzymes have wide range of substrate specificity such as it can degrade other fibrous protein fibrin, elastin, collagen and other non fibrous protein like casein, bovine serum albumin gelatin etc. (Noval et al., 1959; Mukhapadhayay et al., 1989; Dozie et al., 1994; Lin et al., 1995; Letourneau et al., 1998; and Bressollier et al., 1999).

At first Molyneux et al. (1959) attempted to isolate some bacteria that are able to degrade keratin. He isolated organism from the contents of experimentally induced dermoid cysts from mid lateral region of sheep. Examination of wool sample showed degraded wool with numerous corticle and cyticular cells. He found disruption of wool fiber in both in vivo and in vitro. He showed that the organisms belong to genus Bacillus and the organism was capable of attacking native wool protein. The same year Noval et al. (1959) published another article on enzymatic decomposition of native keratin by Streptomyces fradiae. They showed extracellular enzyme secreted by this bacteria capable of degrading the human hair in its native state.

Keratinolytic protein from keratinophilic fungi were reported by Yu et al. (1968), Asahi et al. (1985), and Willams et al. (1989). Mukhopadhay et al. (1989) reported keratinase production by Streptomyces sp. He isolated an inducible extracellular homogenous enzyme, which shows 7.5 fold increases in its activity after DEAE cellulose column chromatography. The enzyme-activity was inhibited by reduced glutathione, PMSF and 2-¬Mercaptaethanol.

Williams et al. (1990) continued his work on enriched feather degrading culture and characterized the organism to its species level for the first time. The microorganisms were identified as Bacillus licheniformis. Lin et al. (1992) purified and characterized keratinase from feather degrading Bacillus licheniformis strain isolated by Williams et al. (1990) with the help of membrane ultra filtration and C-75 gel chromatography. He purified enzyme with 70 fold increased activity. SDS-PAGE analysis revealed that purified keratinase had a molecular weight of 33 kDa. Dozie et al. (1994) reported a thermostable, alkaline-active, keratinolytic proteinasefrom Chrysosporium keratinophylum which was able to solubilize keratin in lactose/mineral salt medium with DMSO. Optimum pH for the enzyme activity was 9 and optimum temperature was 90oC. Wang et al. (1999) scaled up the fermentation condition of keratinase to a pilot scale fermentar. They optimized the fermentation condition to a level of 10-fold increase in enzyme production.

References

1. Hoq MM, Siddiquee KAZ, Kawasaki H and Seki T.2005. Keratinolytic Activity of Some Newly Isolated Bacillus Species. Journal of Biological Science 5(2): 193-200, ISSN1727-3048.

2. Lin X., Lee CG, Casale SE and Shih JC.1992. Purification and characterization of a keratinase from a feather degrading Bacillus Licheniformis strain. J. Appl. Environ. AIlcrobiol. 58 : 3271-3275.

3.Molyneux GS.1959. The digestion of wool by a keratinolytic Bacillus. Aus. J.Biol. Sci, 12: 274-281.

4. Williams CM, Richtcr CS, Mackenzie JR and Shih JCI.1990. Isolation, identification and characterization of a feather-degrading bacterium. J. Appl. Environ. Microbiol. 56: 1509-1515.

English Journal

Nutritional Capability of and Substrate Suitability for Pseudogymnoascus destructans, the Causal Agent of Bat White-Nose Syndrome.

Raudabaugh DB, Miller AN.SourceDepartment of Plant Biology, University of Illinois, Urbana, Illinois, United States of America ; Illinois Natural History Survey, University of Illinois, Champaign, Illinois, United States of America.
PloS one.PLoS One.2013 Oct 21;8(10):e78300. doi: 10.1371/journal.pone.0078300.
Pseudogymnoascus destructans, the causal agent of bat white-nose syndrome, has caused nearly six million deaths in North American bats since its introduction into the United States in 2006. Current research has shown that caves can harbor P. destructans even after the infected bats are removed and b
PMID 24205191

Purification and biochemical characterization of a detergent-stable keratinase from a newly thermophilic actinomycete Actinomadura keratinilytica strain Cpt29 isolated from poultry compost.

Habbeche A, Saoudi B, Jaouadi B, Haberra S, Kerouaz B, Boudelaa M, Badis A, Ladjama A.SourceLaboratory of Applied Biochemistry and Microbiology (LABM), Faculty of Science of Annaba (FSA), Badji Mokhtar-Annaba University, P.O. Box 12, 23000 Annaba, Algeria.
Journal of bioscience and bioengineering.J Biosci Bioeng.2013 Oct 16. pii: S1389-1723(13)00347-2. doi: 10.1016/j.jbiosc.2013.09.006. [Epub ahead of print]
An extracellular thermostable keratinase (KERAK-29) was purified and biochemically characterized from a thermophilic actinomycete Actinomadura keratinilytica strain Cpt29 newly isolated from Algerian poultry compost. The isolate exhibited high keratinase production when grown in chicken feather mea
PMID 24140106

Biotechnological applications and prospective market of microbial keratinases.

Gupta R, Rajput R, Sharma R, Gupta N.SourceDepartment of Microbiology, University of Delhi, South Campus, New Delhi, 110021, India, ranigupta15@rediffmail.com.
Applied microbiology and biotechnology.Appl Microbiol Biotechnol.2013 Oct 13. [Epub ahead of print]
Keratinases are well-recognized enzymes with the unique ability to attack highly cross-linked, recalcitrant structural proteins such as keratin. Their potential in environmental clean-up of huge amount of feather waste has been well established since long. Today, they have gained importance in vario
PMID 24121933

Japanese Journal

異常プリオン分解酵素E77のケラチン分解特性

満生慎二,高杉美佳子,後藤正利 [他]
鹿児島大学農学部学術報告 (59), 37-42, 2009-03
It is suggested that the keratinolytic activity of proteases are associated with the degrading activity of the abnormal type prion protein (PrPSc). We tried to analyze the keratinolytic properties of …
NAID 120001332041