Phytopathology. 1999 Oct;89(10):902-7. doi: 10.1094/PHYTO.1999.89.10.902.
ABSTRACT In this study, we found that the inhibition of fungal growth in potato dextrose broth (PDB) medium by the 14-kDa corn trypsin inhibitor (TI) protein, previously found to be associated with host resistance to aflatoxin production and active against various fungi, was relieved when exogenous alpha-amylase was added along with TI. No inhibitory effect of TI on fungal growth was observed when Aspergillus flavus was grown on a medium containing either 5% glucose or 1% gelatin as a carbon source. Further investigation found that TI not only inhibited fungal production of extracellular alpha-amylase when A. flavus was grown in PDB medium containing TI at 100 mug ml(-1) but also reduced the enzymatic activity of A. flavus alpha-amylase by 27%. At a higher concentration, however, TI stimulated the production of alpha-amylase. The effect of TI on the production of amyloglucosidase, another enzyme involved in starch metabolism by the fungus, was quite different. It stimulated the production of this enzyme during the first 10 h at all concentrations studied. These studies suggest that the resistance of certain corn genotypes to A. flavus infection may be partially due to the ability of TI to reduce the production of extracellular fungal alpha-amylase and its activity, thereby limiting the availability of simple sugars for fungal growth. However, further investigation of the relationship between TI levels and fungal alpha-amylase expression in vivo is needed.
摘要 在这项研究中，我们发现先前发现与宿主对黄曲霉毒素产生抗性相关并能抑制多种真菌的 14kDa 玉米胰蛋白酶抑制剂（TI）蛋白，在添加外源α-淀粉酶的情况下，可以抑制马铃薯葡萄糖肉汤（PDB）培养基中真菌的生长。当在含有 5%葡萄糖或 1%明胶作为碳源的培养基中培养黄曲霉菌时，TI 对真菌生长没有抑制作用。进一步的研究发现，TI 不仅抑制了 TI 浓度为 100μg/ml 的 PDB 培养基中黄曲霉菌产生的胞外α-淀粉酶，而且还降低了黄曲霉菌α-淀粉酶的酶活性 27%。然而，在较高浓度下，TI 会刺激α-淀粉酶的产生。TI 对真菌淀粉代谢中另一种酶——糖化酶的产生的影响则完全不同。在所有研究浓度下，TI 在最初的 10 小时内都能刺激该酶的产生。这些研究表明，某些玉米基因型对黄曲霉菌感染的抗性可能部分归因于 TI 降低了胞外真菌α-淀粉酶的产生及其活性，从而限制了真菌生长所需的简单糖的可用性。然而，仍需要进一步研究 TI 水平与真菌α-淀粉酶在体内表达之间的关系。
