Quantification of human tissue kallikreins in the stratum corneum: dependence on age and gender

Human tissue kallikreins are a family of 15 trypsin or chymotrypsin-like secreted serine proteases (hK1-hK15). hK5, hK6, hK7, hK8, and hK13 have been identified in the stratum corneum (SC), stratum granulosum, and skin appendages. It has been reported that hK5 and hK7 degrade desmosomes/corneodesmosomes, suggesting that kallikreins are responsible for desquamation. We report the quantification of hK5, hK6, hK7, hK8, hK10, hK11, hK13, and hK14 in the SC by ELISA and their variation among age groups. The total SC trypsin and chymotrypsin-like activities were also measured. The amount of hK7, hK8, and hK11 (ng per mg dry weight) were high, and varied from 6 to 14, hK5 (2.0-4.0) was present at intermediate levels, and hK10 (0.65-1.0), hK14 (0.1-0.3), hK6 (0.1-0.3), and hK13 (0.02-0.1) were present at lower levels. hK6 and hK14 were significantly lower in females between 20 and 59 y. hK5, hK7, hK10, hK11, and hK14 were not significantly different across the age groups. hK8 was lowest at extremes of age (highest at 30-39 y), hK6 was lower at >30 y, and hK13 was lower at >20 y. Overall trypsin-like activity did not differ across age groups but was higher in subjects <11 y. Overall chymotrypsin-like activity was not related to age. In conclusion, we found multiple kallikreins in the SC and suggest that these enzymes may be responsible for desquamation through an enzymatic cascade pathway.