Hand D, Elliott B M, Griffin M
Department of Life Sciences, Trent Polytechnic, Nottingham, U.K.
Biochim Biophys Acta. 1988 Jun 30;970(2):137-45. doi: 10.1016/0167-4889(88)90172-3.
Transglutaminase (EC 2.3.2.13) activity in chemically induced rat hepatocellular carcinomas was reduced by some 65% when compared to normal rat livers. The majority of the remaining activity (approx. 85%) was found in the particulate fraction. The use of non-ionic detergent to extract the transglutaminase activity present in both normal and tumour tissue followed by its separation on a Mono-Q column revealed two distinct peaks of activity. These peaks of activity were equivalent to those previously identified as a membrane-bound transglutaminase and the more characteristic cytosolic or tissue transglutaminase. The ratio of the activity of the cytosolic enzyme to that of the membrane-bound enzyme in normal liver was calculated as 5:1. In hepatocellular carcinomas, this ratio was reduced to 0.4:1. No significant change in the activity of the membrane-bound enzyme was detectable in tumour tissue. Comparison of the cytosolic enzyme found in hepatocellular carcinomas with that found in normal liver indicated no change in its molecular weight, Km,app for putrescine incorporation into N,N'-dimethylcasein and sensitivity to activation by Ca2+. These observations suggest that the reduction in transglutaminase activity observed in the hepatocellular carcinoma is due to a selective reduction in the expression of the cytosolic transglutaminase.
与正常大鼠肝脏相比，化学诱导的大鼠肝细胞癌中的转谷氨酰胺酶（EC 2.3.2.13）活性降低了约65%。其余大部分活性（约85%）存在于颗粒部分。使用非离子洗涤剂提取正常组织和肿瘤组织中的转谷氨酰胺酶活性，然后在Mono-Q柱上进行分离，结果显示有两个不同的活性峰。这些活性峰与先前鉴定为膜结合转谷氨酰胺酶和更具特征性的胞质或组织转谷氨酰胺酶的峰相当。正常肝脏中胞质酶与膜结合酶的活性比经计算为5:1。在肝细胞癌中，该比例降至0.4:1。在肿瘤组织中未检测到膜结合酶的活性有显著变化。对肝细胞癌中发现的胞质酶与正常肝脏中发现的胞质酶进行比较，结果表明其分子量、将腐胺掺入N,N'-二甲基酪蛋白的表观Km以及对Ca2+激活的敏感性均无变化。这些观察结果表明，在肝细胞癌中观察到的转谷氨酰胺酶活性降低是由于胞质转谷氨酰胺酶表达的选择性降低所致。
