<；P>；PROBLEM TO BE SOLVED: To provide a skin keratinization promoter useful for improving the barrier function of the skin and preventing the aging of the skin. <；P>；SOLUTION: The skin keratinization promoter includes a nacrein protein which a shell or a pearl fragment of Pictada martensil or a powder thereof produces and this nacrein protein is (I) a protein obtained by extracting a substance obtained by decalcifying Pictada martensil or the like with a chelating agent or (II) a protein produced by genetic engineering utilizing this extracted substance and at least one host cell selected from Escherichia coli, yeast, and a cocoon. <；P>；COPYRIGHT: (C)2011,JPO&INPIT
