Docherty K, Hutton J C, Steiner D F
J Biol Chem. 1984 May 25;259(10):6041-4.
The distribution of proteases potentially reactive with peptide sequences containing pairs of basic amino acids or single basic amino acids was studied in subcellular fractions of a transplantable rat insulinoma using the affinity probes 125I-Tyr-Ala-Lys- ArgCH2Cl and 125I-Tyr-Ala-norleucine- ArgCH2Cl . Both probes labeled predominantly proteins of Mr = 39,000, 31,500, and 25,000. The Mr = 25,000 component appeared to be of lysosomal origin, while the Mr = 39,000 and 31,500 proteins were present in both the lysosomes and insulin granules. The Mr = 39,000 and 31,500 proteins were identified as precursor/product forms of the cysteine protease cathepsin B, while assays performed with fluorigenic peptide substrates suggested that the Mr = 25,000 protein was probably cathepsin L and/or H. The greater reactivity of the Mr = 39,000 form with the dibasic probe suggests that the relative proportions of the Mr = 39,000 and 31,500 forms of cathepsin B in different organelles may determine the extent to which the enzyme expresses activity as a specific (prohormone processing) endopeptidase or a more general (degradative) peptidase.
使用亲和探针125I-Tyr-Ala-Lys-ArgCH2Cl和125I-Tyr-Ala-正亮氨酸-ArgCH2Cl，研究了可移植大鼠胰岛素瘤亚细胞组分中可能与含双碱性氨基酸对或单碱性氨基酸的肽序列发生反应的蛋白酶分布情况。两种探针主要标记分子量为39,000、31,500和25,000的蛋白质。分子量为25,000的组分似乎起源于溶酶体，而分子量为39,000和31,500的蛋白质同时存在于溶酶体和胰岛素颗粒中。分子量为39,000和31,500的蛋白质被鉴定为半胱氨酸蛋白酶组织蛋白酶B的前体/产物形式，而用荧光肽底物进行的测定表明，分子量为25,000的蛋白质可能是组织蛋白酶L和/或H。分子量为39,000的形式与双碱性探针的反应性更强，这表明组织蛋白酶B的分子量为39,000和31,500的形式在不同细胞器中的相对比例可能决定该酶作为特异性（激素原加工）内肽酶或更普遍（降解性）肽酶表达活性的程度。
