【项目简介】
Cystatin E/M, also referred to as CST6, is a member of type 2 cysteine proteinase inhibitors of the cystatin superfamily, and inhibits papain and cathepsin B. Cystatin E is a low molecular mass secreted protein existing in both a glycosylated (17 kDa) and an unglycosylated (14 kDa) form, with two characteristic intrachain disulfide bridges. Expression of cystatin M/E is found to be restricted to the epidermis, more specifically in the stratum granulosum, sweat glands, sebaceous glands, and the hair follicles. In addition to its function as a cysteine protease inhibitor, cystatin M/E also serves as a target for cross-linking by transglutaminases. Accordingly, cystatin M/E was suggested to be involved in barrier formation and maintenance. Furthermore, studies have revealed that cystatin M/E is frequently epigenetically inactivated during breast carcinogenesis, and thus be regarded as a candidate of tumour suppressor gene.
 
【检验原理】
本试剂盒采用双抗体夹心ELISA法。酶标微孔板上预包被有抗人Cystatin E抗体，当加入标准品和待测样本时，标准品和待测样本中的人Cystatin E会和该抗体结合。洗板后，游离的其他成分被洗去，加入辣根过氧化物酶标记的的抗人Cystatin E抗体可与被酶标板捕获的人Cystatin E结合，形成“包被抗人Cystatin E抗体+人Cystatin E+抗人Cystatin E抗体-HRP”免疫复合物。当加入TMB显色底物后，复合物上连接的HRP催化底物反应，生成蓝色产物，终止反应后变为黄色。在450nm处测定OD值，人Cystatin E浓度与OD450值之间呈正比，可通过绘制标准曲线求出标本中人Cystatin E的浓度。