Kaneda M, Sobue A, Eida S, Tominaga N
J Biochem. 1986 Feb;99(2):569-77. doi: 10.1093/oxfordjournals.jbchem.a135513.
Seven proteinases were isolated from the fruit of snake-gourd, Trichosanthes cucumeroides Maxim. Their isozymes are all serine proteinases, and homologous in their respective molecular weights, amino acid compositions, and enzymatic properties. Their molecular weight was estimated to be about 50,000. Using casein as a substrate, the maximum activity was found in the alkaline pH region. The optimum temperature using casein was 70 degrees C at pH 7.3. The enzymes were strongly inhibited by diisopropyl fluorophosphate and not inhibited by inhibitors of sulfhydryl or metalloproteases. The reduced and S-carboxymethylated insulin B-chain was used as a substrate in an investigation of the specificity. The enzyme was found to have a wide specificity for this substrate but preferentially hydrolyzed the peptide bonds involving the carboxyl groups of charged amino acid such as S-cm-cysteine, glutamic acid, histidine, arginine, and lysine. Experimental evidence indicated that the snake-gourd proteinases are similar in their properties to cucumisin, which is isolated from the sarcocarp of melon fruit.
从栝楼（Trichosanthes cucumeroides Maxim.）果实中分离出了七种蛋白酶。它们的同工酶均为丝氨酸蛋白酶，在各自的分子量、氨基酸组成和酶学性质方面具有同源性。其分子量估计约为50,000。以酪蛋白为底物时，在碱性pH区域发现最大活性。以酪蛋白为底物时，最适温度在pH 7.3时为70℃。这些酶受到二异丙基氟磷酸的强烈抑制，不受巯基或金属蛋白酶抑制剂的抑制。在特异性研究中，使用还原型和S-羧甲基化胰岛素B链作为底物。发现该酶对该底物具有广泛的特异性，但优先水解涉及带电荷氨基酸羧基的肽键，如S-cm-半胱氨酸、谷氨酸、组氨酸、精氨酸和赖氨酸。实验证据表明，栝楼蛋白酶的性质与从甜瓜果肉中分离出的黄瓜蛋白酶相似。
