Keratins are cystine-rich proteins associated with intermediate filaments (IFs) which are cytoskeleton element having diameter of 8-10nm It is available in two forms a- and B-keratins. a-keratins are copiously found in the soft tissues such as sheep wool, hair, and skin. These are rich in cystine. B-keratins are present in hard tissue protein of nails, fish scales, bird feathers, and others. They are rich in glycine and alanine, poor in cystine, hydroxyproline, and proline