Negi M, Matsui T, Ogawa H
J Invest Dermatol. 1981 Nov;77(5):389-92. doi: 10.1111/1523-1747.ep12494561.
The activity of crude human epidermal transglutaminase was enhanced remarkably following 24 hr preincubation at low pH (pH 4.5), whereas the pure human epidermal transglutaminase did not show enhancement of enzyme activity at low pHs. Preincubation of pure transglutaminase with rat liver lysosomal fractions (100 microgram/ml) caused a time-dependent enhancement of activity at pH 4.5, up to 4.5 times of the initial activity. This enhancement was specific for lysosomal fractions among the several rat liver subcellular fractions tested. The activity of purified transglutaminase stimulated by lysosomal fractions was inhibited by pepstatin (50 microgram/ml), chymostatin (50 microgram/ml) and EDTA (1 mM). Preincubation of purified transglutaminase with 5 to 100 microgram/ml cathepsin D caused a time-dependent enhancement of activity up to 9.5-fold over control. This enhancement was specific for cathepsin D among the several lysosomal enzymes tested. These in vitro observations suggest possible activation mechanisms of epidermal transglutaminase in vivo. Epidermal transglutaminase may be activated by lysosomal acid proteinases, such as cathepsin B1 and cathepsin D, which are released and activated during the autolytic stages in granular layer in epidermis.
在低pH值（pH 4.5）下预孵育24小时后，粗制人表皮转谷氨酰胺酶的活性显著增强，而纯人表皮转谷氨酰胺酶在低pH值下未表现出酶活性增强。将纯转谷氨酰胺酶与大鼠肝脏溶酶体组分（100微克/毫升）预孵育，在pH 4.5时导致活性呈时间依赖性增强，最高可达初始活性的4.5倍。在所测试的几种大鼠肝脏亚细胞组分中，这种增强对溶酶体组分具有特异性。溶酶体组分刺激的纯化转谷氨酰胺酶活性受到胃蛋白酶抑制剂（50微克/毫升）、糜蛋白酶抑制剂（50微克/毫升）和EDTA（1毫摩尔）的抑制。将纯化的转谷氨酰胺酶与5至100微克/毫升组织蛋白酶D预孵育，导致活性呈时间依赖性增强，最高比对照高9.5倍。在所测试的几种溶酶体酶中，这种增强对组织蛋白酶D具有特异性。这些体外观察结果提示了表皮转谷氨酰胺酶在体内可能的激活机制。表皮转谷氨酰胺酶可能被溶酶体酸性蛋白酶激活，如组织蛋白酶B1和组织蛋白酶D，它们在表皮颗粒层自溶阶段释放并被激活。
