Technical Research Centre of Finland, Biotechnical Laboratory, Helsinki 18, Finland.
Plant Physiol. 1976 Jun;57(6):867-71. doi: 10.1104/pp.57.6.867.
A peptidase hydrolyzing the dipeptide Ala-Gly optimally at pH 8 to 9 was purified about 3500-fold from germinated grains of barley (Hordeum vulgare L.). According to disc electrophoresis in the presence of sodium dodecyl sulfate, the preparation was about 90% pure.The enzyme preparation hydrolyzed all of the 15 neutral dipeptides tested, but showed no activity on Lys-Gly or Asp-Ala. Three tripeptides and four synthetic aminopeptidase substrates were hydrolyzed at less than 0.1% of the rate for Ala-Gly; inhibition and inactivation tests indicated that these reactions were due to some contaminating aminopeptidase(s). The results suggest that the purified enzyme is a specific dipeptidase. Km values were determined for six dipeptides at pH 8.8; they varied from 0.3 to 15.8 mm. The enzyme was strongly inhibited both by metal chelators and by sulfhydryl reagents. The elution volumes of the enzyme in gel chromatography on Sephadex G-150 and Ultrogel AcA 22 corresponded to molecular weight 130,000 and 175,000, respectively. The migration rate in sodium dodecyl sulfate disc electrophoresis indicated a subunit molecular weight of 50,000.The barley enzyme is remarkably similar to several mammalian and microbial dipeptidases.
从发芽的大麦（Hordeum vulgare L.）种子中纯化出一种在 pH8 到 9 之间最适水解二肽 Ala-Gly 的肽酶，其比活提高了约 3500 倍。根据十二烷基硫酸钠存在下的圆盘电泳，该制剂约为 90%纯。酶制剂水解了所有测试的 15 种中性二肽，但对 Lys-Gly 或 Asp-Ala 没有活性。三种三肽和四种合成氨肽酶底物的水解速率仅为 Ala-Gly 的 0.1%以下；抑制和失活试验表明，这些反应是由于一些污染的氨肽酶所致。结果表明，纯化的酶是一种特异性二肽酶。在 pH8.8 下测定了六种二肽的 Km 值；它们的范围从 0.3 到 15.8mm。该酶被金属螯合剂和巯基试剂强烈抑制。该酶在 Sephadex G-150 和 Ultrogel AcA22 上的凝胶层析中的洗脱体积分别对应于分子量 130000 和 175000。在十二烷基硫酸钠圆盘电泳中的迁移率表明亚基分子量为 50000。大麦酶与几种哺乳动物和微生物的二肽酶非常相似。
