Centro de Investigación en Alimentación y Desarrollo AC (CIAD), Hermosillo, Sonora, Mexico.
Phytochemistry. 2010 Apr;71(5-6):515-23. doi: 10.1016/j.phytochem.2009.12.005. Epub 2010 Jan 14.
Aspartic proteinases (APs) are involved in several physiological processes in plants, including protein processing, senescence, and stress response and share many structural and functional features with mammalian and microbial APs. The heterodimeric aspartic proteinase A1 from Arabidopsis thaliana (AtAP A1) was the first acid protease identified in this model plant, however, little information exists regarding its structure function characteristics. Circular dichroism analysis indicated that recombinant AtAP A1 contained an higher alpha-helical content than most APs which was attributed to the presence of a sequence known as the plant specific insert in the mature enzyme. rAtAP A1 was stable over a broad pH range (pH 3-8) with the highest stability at pH 5-6, where 70-80% of the activity was retained after 1 month at 37 degrees C. Using calorimetry, a melting point of 79.6 degrees C was observed at pH 5.3. Cleavage profiles of insulin beta-chain indicated that the enzyme exhibited a higher specificity as compared to other plant APs, with a high preference for the Leu(15)-Tyr(16) peptide bond. Molecular modeling of AtAP A1 indicated that exposed histidine residues and their interaction with nearby charged groups may explain the pH stability of rAtAP A1.
天冬氨酸蛋白酶（APs）参与植物中的几种生理过程，包括蛋白质加工、衰老和应激反应，并且与哺乳动物和微生物 APs 具有许多结构和功能特征。拟南芥（AtAP A1）的异二聚体天冬氨酸蛋白酶 A1 是该模式植物中鉴定的第一种酸性蛋白酶，但是，关于其结构功能特征的信息很少。圆二色性分析表明，重组 AtAP A1 比大多数 APs 具有更高的α-螺旋含量，这归因于成熟酶中存在称为植物特异性插入的序列。rAtAP A1 在较宽的 pH 范围内（pH 3-8）稳定，在 pH 5-6 时稳定性最高，在 37°C 下放置 1 个月后保留 70-80％的活性。使用量热法，在 pH 5.3 时观察到 79.6°C 的熔点。胰岛素β链的切割图谱表明，与其他植物 APs 相比，该酶表现出更高的特异性，对 Leu（15）-Tyr（16）肽键具有较高的偏好性。AtAP A1 的分子建模表明，暴露的组氨酸残基及其与附近带电基团的相互作用可以解释 rAtAP A1 的 pH 稳定性。
