Title: Keratinase
CAS Registry Number: 9025-41-6
Additional Names: M-Zyme
Literature References: A proteolytic enzyme, commercially produced by a strain of Streptomyces fradiae: Nickerson, Noval, US 2988487 (1961 to Rutgers Res. and Educ. Found.). Can convert about 50% of the dry wt of wool into a water-sol form, permitting hair separation from hides. The amount of enzyme needed to dehair hides is not enough to cause much digestion of the hair itself, which is recovered and used in felt making. The enzyme attacks at the base of the hair shaft, which is particularly sensitive to the action of keratinase.
Properties: Soluble in water. Non-dialyzable. Optimum efficiency at pH 8.5-9.5. Becomes inactive by heating to 100° for 5 min. The ability to digest keratin appears to be dependent on the presence of at least trace amounts of metal ions which form chelates.
Use: In the dehairing of hides and skins: Robison, Nickerson, US 2988488 (1961 to Mearl). In depilatory compositions for human use: Mattin, Greenstein, US 2988485 (1961 to Mearl).
Kermesic Acid Kerosene Ketamine Ketanserin Ketazolam

Keratinases are proteolytic enzymes in nature. It was classified as proteinase 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 of the worker defined keratinase as 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. It mainly attacks on the disulfide (-S-S-) bond of the keratin substrate (Bockel et al., 1995). The keratinase productions by various microorganisms were reported by a number of workers. It was found that keratinase produce by 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.