Hejgaard J, Jacobsen S, Svendsen I
Department of Biochemistry and Nutrition, Technical University of Denmark, Lyngby.
FEBS Lett. 1991 Oct 7;291(1):127-31. doi: 10.1016/0014-5793(91)81119-s.
Antifungal activity has been associated with 2 immunochemically distinct proteins, protein R and S (Mr approximately 23 kDa; pI 9-10), which were isolated in pure form from barley grain. The proteins are homologous with thaumatin- and pathogenesis-related proteins of the PR5 family. The proteins inhibit growth of i.a. Trichoderma viride and Candida albicans in microtiter plate assays and act synergistically with barley grain chitinase C. Like maize zeamatin, protein R and S but not chitinase C retarded fungal growth in synergism with nikkomycin Z, a nucleoside-peptide inhibitor of fungal chitin synthesis. Although no inhibition of alpha-amylases or serine proteases could be associated with protein R or S the results indicate that the homologous maize grain bifunctional inhibitor of insect alpha-amylase and trypsin is very similar to or identical with maize zeamatin, which was proposed to have permeabilizing activity towards fungal membranes. Thus, in addition to the intensely sweet properties of thaumatin, multiple unrelated defense functions against insect and fungal pests can now be associated with the family of thaumatin-homologous proteins.
抗真菌活性与两种免疫化学性质不同的蛋白质有关，即蛋白质R和S（分子量约为23 kDa；等电点9 - 10），它们是从大麦籽粒中以纯形式分离出来的。这些蛋白质与PR5家族的奇异甜蛋白和病程相关蛋白同源。在微量滴定板试验中，这些蛋白质能抑制包括绿色木霉和白色念珠菌在内的真菌生长，并与大麦籽粒几丁质酶C协同作用。与玉米玉米素一样，蛋白质R和S而非几丁质酶C与真菌几丁质合成的核苷肽抑制剂多氧霉素Z协同作用，抑制真菌生长。尽管蛋白质R或S与α -淀粉酶或丝氨酸蛋白酶的抑制作用无关，但结果表明，玉米籽粒中对昆虫α -淀粉酶和胰蛋白酶具有双功能抑制作用的抑制剂与玉米玉米素非常相似或相同，玉米玉米素被认为对真菌膜具有通透活性。因此，除了奇异甜蛋白强烈的甜味特性外，现在可以将针对昆虫和真菌害虫的多种不相关的防御功能与奇异甜蛋白同源蛋白家族联系起来。
