Castle J D, Cameron R S, Patterson P L, Ma A K
J Membr Biol. 1985;87(1):13-26. doi: 10.1007/BF01870695.
Heterologous antibodies to gamma-glutamyl transferase (gamma GT), an ectoenzyme associated with the apical surface of many types of epithelial cells involved in secretion and transport, have been used to identify and partially characterize the spectrum of antigens in a series of epithelial tissues that exhibit a range of enzyme activities. In addition to antigens corresponding to the subunits of the active enzyme (mol wt 55K, 30K), antigens of mol wt approximately 85-greater than or equal to 95K have been detected using an antibody raised against the enzyme purified in nonionic detergent. The latter species are shown to share antigenic determinants with and to be structurally related to the enzyme subunits; however, they do not blind significantly to antibodies raised to protease-solubilized gamma GT. Further, they constitute the major antigens in tissues that exhibit relatively low levels of enzyme activity. These polypeptides are apparently larger than a recently characterized biosynthetic precursor of the gamma GT subunits. Although they do not have gamma GT activity themselves and their function is undefined, the possibility that they may represent highly glycosylated polypeptides related either to gamma GT precursors (that persist without processing) or to the large enzyme subunit merits consideration.
γ-谷氨酰转移酶（γGT）是一种与参与分泌和转运的多种上皮细胞顶端表面相关的外切酶，针对它的异源抗体已被用于识别和部分表征一系列表现出不同酶活性的上皮组织中的抗原谱。除了与活性酶亚基（分子量55K、30K）相对应的抗原外，使用针对在非离子去污剂中纯化的该酶产生的抗体，还检测到了分子量约为85 - 大于或等于95K的抗原。后一类抗原显示与酶亚基具有共同的抗原决定簇且在结构上相关；然而，它们与针对蛋白酶溶解的γGT产生的抗体结合不明显。此外，它们是酶活性相对较低的组织中的主要抗原。这些多肽显然比最近表征的γGT亚基的生物合成前体更大。尽管它们本身没有γGT活性且其功能尚不清楚，但它们可能代表与γGT前体（未经加工而留存）或大酶亚基相关的高度糖基化多肽的可能性值得考虑。
