KERATINIZATION is one of the most important metabolic functions of the epidermis. Although numerous investigators have studied the nature of the changes which the proteins of the living cells of the Malpighian layer undergo during the transition to keratinized structures, the exact chemical features of this transformation remain elusive.
One of the most characteristic chemical changes in keratinization involves the sulfur-containing amino acids. Most of the sulfur in keratin occurs in the form of cystine; the disulfide bridges of cystine account for much of the stability and chemical resistance of keratin.
The disulfide bridges in keratin have been generally assumed to result from the oxidation of the sulfhydryl groups of cysteine, found in the stratum Malpighii as follows:
This view was based largely on histochemical evidence. When sections of the epidermis were stained with sodium nitroprusside, a histochemical sulfhydryl reagent, only the cells of the Malpighian layer stained
VAN SCOTT EJ, FLESCH P. SULFHYDRYL GROUPS AND DISULFIDE LINKAGES IN NORMAL AND PATHOLOGICAL KERATINIZATION. AMA Arch Derm Syphilol. 1954;70(2):141–154. doi:10.1001/archderm.1954.01540200001001
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