Studies on the Biochemistry of Epidermis IV. The Free Amino Acids, Ammonia, Urea, and Pyrrolidone Carboxylic Acid Contest of Conventional and Germ-Free Albino Guinea Pig Epidermis

Impact of Stratum Corneum Damage on Natural Moisturizing Factor (NMF) in the Skin

“…A reduction in arginine following SLS exposure appears to coincide with an increase in ornithine and urea [34][35][36] , the products of arginasemediated breakdown of arginine [ 55 ] . This suggests an increase in arginase activity.…”

“…Altered conditions of pH, ion concentrations, or substrate may explain the increase in arginase activity under damaged conditions. Also coinciding with decreased arginine and increased ornithine levels is a decrease in citrulline, implying a reduction in the activity of ornithine carbamoyltransferase, the enzyme responsible for converting ornithine to citrulline during urea cycling [ 55 ] . A similar response is observed following UV damage, with increased trans -Urocanic levels coinciding with decreased histidine [ 37 ] , implying an increase in histidine breakdown with UV-mediated disruption (Fig .…”

UVB-Shielding Effects of para-Coumaric Acid

“…These reactions are catalyzed by L-tyrosine ammonia lyase, L-phenylalanine ammonia lyase, L-histidine ammonia lyase (also called histidase) and L-tryptophan ammonia lyase that are distributed in prokaryotes, plants or animals [17,18]. Of these compounds, UCA has attracted an attention in dermatology and cosmetics fields as a natural sunscreen since it was identified as the major acid-soluble, UVabsorbing compound in the stratum corneum [19,20]. The photon energy absorbed by UCA is effectively dissipated through the reversible isomerization to cis-urocanic acid [21,22].…”

Morphological and Biochemical Changes in Epidermal Nuclei and Nucleic Acid Following Ultraviolet Exposure

“…W ith m ore in te n se irra d ia tio n the R N A c o n te n t decreased, a u ltra m ic ro tech n iq u e using u ltra v io le t a b so rp tio n , agreed w ith p re v io u s nucleic acid analyses b ased on p h o sp h o ru s c o n te n t [12], u ltra v io le t absorbance [13,16], a n d su g ar c o n te n t [14,15].…”