Keratinase
Keratinases are proteolytic enzymes that digest keratin.[1]
History
They were initially classified as 'proteinases of unknown mechanism' by the Nomenculture Committee on the International Union of Biochemistry in 1978 with
Function
Keratinases are produced only in the presence of keratin-containing substrate. The primary catalytic mechanism consists of serine protease activity combined with high specificity for compact substrates and exposed active sites. Additional disulfide bond cleavage by other means is often required for complete degradation.
Distribution
At first Molyneux et al. (1959) attempted to isolate some bacteria that are able to degrade keratin.[3] He isolated organisms 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 these 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 homogeneous enzyme, which shows a 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.
