The gene of the protease inhibitor SKALP/elafin is a member of the REST gene family.

Members of the REST gene family characteristically have a transcription unit consisting of three exons. The first and the last exon are conserved among members, while the second exon--encoding almost all of the mature protein--differs considerably. The so far known REST genes are highly, and almost exclusively, expressed in the seminal vesicles. By sequence analysis we have now identified the gene for the protease inhibitor SKALP/elafin as a new member of the REST gene family. The protein is expressed in the epidermis and serves, like the product of several REST genes, as substrate for transglutaminase. We have also found what seems to be a locus encompassing both transglutaminases and REST genes centered around the region q12 on the human chromosome 20, raising the question whether the enzymes and substrates have evolved in parallel.