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LOCALIZATION AND POSSIBLE ACTIVATION MECHANISMS OF TRANSGLUTAMINASE IN THE SKIN
Author(s) -
Negi Makoto
Publication year - 1983
Publication title -
the journal of dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 65
eISSN - 1346-8138
pISSN - 0385-2407
DOI - 10.1111/j.1346-8138.1983.tb01114.x
Subject(s) - stratum corneum , tissue transglutaminase , chemistry , enzyme assay , biochemistry , enzyme , pepstatin , biology , genetics , protease
The activity of transglutaminase per unit of wet weight, dry weight, soluble protein, and DNA was determined in three fractions (stratum corneum, malpighii, and dermis) of cow snout skin. The stratum corneum showed the highest enzyme activity among these three fractions. The activity of transglutaminase in the stratum malpighii was ehhanced remarkably by a 36 hour preincubation period at pH 4.5, but the activity in the stratum corneum did not show any increase in enzyme activity under acidic conditions. This ehhancement of enzyme activity was inhibited by pepstatin (100 μ g/ml) and chymostatin (100 μ g/ml). Relatively high activities of lysosomal enzymes such as β ‐glucuronidase, cathepsin B 1 , and cathepsin D were detected in the stratum malpighii fraction, but these enzyme activities were low in the stratum corneum fraction. To further clarify the nature and activation systems of transglutaminase from stratum corneum and malpighii, transglutaminase solutions with the same activity were prepared from the two layers. Then the same amount of cathepsin D in the crude malpighian transglutaminase solution was added in the crude transglutaminase solution of stratum corneum. Following incubation, the transglutaminase activity of stratum corneum became elevated to the same level of enzyme activity as that of the stratum malpighii. These results suggest the importance of cathepsin D in the activation system of transglutaminase and possible activation machanisms of epidermal transglutaminase in vivo . Transglutaminase in the stratum malpighii may exist in a nonactivated form. During the autolytic stages in the stratum granulosum, a small amount of this nonactivated transglutaminase may be activated by released lysosomal acid proteinases such as cathepsin B 1 and cathepsin D. Thereafter, activated transglutaminase could catalyze the formations of ε ‐( γ ‐glutamyl) lysine cross‐linking in the proteins synthesized in the cytosol of keratinizing cells with ultimate transformation to the membrane‐lining protein, the so‐called marginal band. In addition, most of the transglutaminase in the stratum corneum may still remain in a nonactivated form, since cathepsin D like enzymes may possibly be inactivated or degraded in the stratum corneum in vivo .