Department of Biology, The Colorado College, Colorado Springs, Colorado 80903.
Plant Physiol. 1985 Nov;79(3):641-5. doi: 10.1104/pp.79.3.641.
One major and two minor aminopeptidase activities from germinated jojoba (Simmondsia chinensis) cotyledon extracts were separated by ammonium sulfate precipitation and chromatofocusing. None of the activities were inhibited by 1,10 phenanthroline.The major aminopeptidase, purified 260-fold, showed a pH optimum of 6.9 with leucine-p-nitroanilide as substrate, a molecular weight estimated at 14,200 by electrophoretic analysis, and an isoelectric point of 4.5 according to the chromatofocusing pattern. Activity was inhibited by p-chloromercuribenzoate, slightly stimulated by 1,10 phenanthroline and 2-mercaptoethanol, and not influenced by Mg(2+) or diethyl pyrocarbonate. Inhibition by p-chloromercuribenzoate was prevented by the presence of cysteine in the assay. Leucine-p-nitroanilide and leucine-beta-naphthylamide were the most rapidly hydrolyzed of 11 carboxy-terminal end blocked synthetic substrates tested. No activity on endopeptidase or carboxypeptidase specific substrates was detected. The major aminopeptidase showed activity on a saline soluble, jojoba seed protein preparation and we suggest a possible physiological role for the enzyme in the concerted degradation of globulin reserve proteins during cotyledon senescence.
从发芽的霍霍巴（西蒙得西亚 chinensis）子叶提取物中分离出一种主要的和两种次要的氨肽酶活性，通过硫酸铵沉淀和等电聚焦进行分离。这些活性都不受 1,10 菲咯啉的抑制。主要的氨肽酶经过 260 倍的纯化，在以亮氨酸 -p-硝基苯胺为底物时表现出最适 pH 值为 6.9，电泳分析估计分子量为 14,200，根据等电聚焦图谱的模式等电点为 4.5。该活性被对氯汞苯甲酸抑制，被 1,10 菲咯啉和 2-巯基乙醇轻微刺激，不受 Mg(2+)或二乙基焦碳酸盐的影响。在测定中存在半胱氨酸时，对氯汞苯甲酸的抑制作用被阻止。在测试的 11 种羧基末端封闭的合成底物中，亮氨酸 -p-硝基苯胺和亮氨酸 -β-萘基酰胺被水解最快。未检测到对内肽酶或羧肽酶特异性底物的活性。主要的氨肽酶对盐溶性霍霍巴种子蛋白制剂具有活性，我们建议该酶在子叶衰老过程中协同降解球蛋白储备蛋白方面可能具有生理作用。
