Keratin

Protein in the upper layer of the skin, hair, nails and animal horns. The word keratin comes from the Indo-European ker meaning horn.

* * *

Collective name for a group of proteins that form the intermediate filaments in epithelial cells. Keratins have a molecular weight between 40 kd and 68 kd, and are separated one from another by electrophoresis and isoelectric focusing; thus separated, they are sequentially numbered from 1–20, and also subdivided into low, intermediate, and high molecular weight proteins. According to their isoelectric mobility they are either acidic or basic. In general, each acidic k. protein has its basic equivalent with which it is paired to form the intermediate filaments; some k. proteins, however, occur unpaired. Various epithelial cells contain different k. proteins, in a tissue-specific manner. Antibodies to k. proteins are widely used for histologic typing of tumors, and are especially useful for distinguishing carcinomas from sarcomas, lymphomas, and melanomas. SYN: ceratin, cytokeratin. [G. keras (kerat-), horn, + -in]

* * *

ker·a·tin 'ker-ət-ən n any of various sulfur-containing fibrous proteins that form the chemical basis of horny epidermal tissues (as hair and nails) and are typically not digested by enzymes of the gastrointestinal tract see PSEUDOKERATIN

* * *

n.

one of a family of proteins that are the major constituents of the nails, hair, and the outermost layers of the skin. The cytoplasm of epithelial cells, including keratinocyte, contains a network of keratin filaments.

* * *

ker·a·tin (kerґə-tin) any of a family of scleroproteins that form the primary constituents of epidermis, hair, nails, and horny tissues. Included are the cytokeratins of epithelial tissue and the hard keratins of ectodermally derived structures such as hair and nails. Because it is insoluble in gastric juice, keratin is sometimes used to coat pills designed to pass through the stomach and dissolve in the intestine.