Cathepsin L activity analysis method for evaluation of skin conditions of human

In order to develop an analysis method of skin conditions for humans, we have been investigating cathepsin L (Cat L) activity derived from stratum corneum as a biomarker. In the present work, an analysis method for a low amount of Cat L activity was demonstrated that was made possible by collecting stratum corneum using a tape stripping, concentrating stratum corneum sample solution and using an inhibitor and a fluorescent substrate of Cat L. Within the range of Cat L activity between 0.003 and 0.04 U/L, the calibration curve for this method showed coefficient with R ² = 0.98. The Cat L activity ranged between 0.005 and 0.028 U/L in all of the stratum corneum samples in the subjective evaluation. It was indicated that this analysis method had a sufficient range for the analysis of human Cat L activity. The determined coefficient between the Cat L activity and the total protein showed 0.09, which was a comparatively low level. Therefore, it was considered that the Cat L/total protein ratio might be a useful index of the skin condition for humans. Thus, it was indicated that this analysis method might be suitable for an easy analysis of Cat L activity.