BIOSYNTHESIS OF PYRROLIDONE CARBOXYLIC-ACID IN HAIRLESS MOUSE EPIDERMIS

[摘要] [3H]Glutamic acid incorporation in vivo into hairless mouse epidermal pyrrolidone carboxylic acid (PCA) was followed with time after a single s.c. injection. PCA specific activity increased slowly, reaching a peak at 3-4 days after injection of the labeled amino acid, after which it slowly declined. Incorporation of [3H]glutamic acid into epidermal PCA was markedly inhibited by a single topical application of cycloheximide. Topical application of cycloheximide 2 h prior to [3H]glutamate injection caused a significantly greater reduction in PCA specific activity (determined 3 days after injection) than cycloheximide treatment 3 h after administration of the labeled amino acid. Of the PCA content of hairless mouse epidermis, 97% resided in the stratum corneum. These observations indicate the involvement of protein synthesis in the formation of PCA from glutamic acid rather than a direct conversion of the amino acid. The high level of PCA in mammalian epidermis appears to be caused by its accumulation in the stratum corneum accompanied by a relatively slow rate of PCA turnover in comparison to other tissues.