A Corn Trypsin Inhibitor with Antifungal Activity Inhibits Aspergillus flavus α-Amylase

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.

A Kunitz trypsin inhibitor from chickpea (<i>Cicer arietinum</i> L.) that exerts an antimicrobial effect on Fusarium oxysporum f.sp. ciceris

“…The results obtained using conidial germination and hyphal growth was in correlation to each other as the results showed inhibition in the presence of trypsin inhibitor were consistent (Figures 7 and 8). These studies were similar to Chen et al [21] reports, which showed that the resistance of certain corn genotypes to fungal infection is related to the action of trypsin inhibitor, which is due to the lowering in the production and activity of fungal alpha-amylase, which in turn reduce the availability of simple sugars for fungal growth. Similar studies on the inhibition of spore germination and mycelium growth of Alternaria alternata by buckwheat trypsin/chymotrypsin was observed [22].…”

“…Likewise, cysteine proteinase inhibitors from pearl millet also inhibited the growth of many pathogenic fungi including Trichoderma reesei [23]. In addition, the antifungal effect of trypsin inhibitor was observed in wheat kernel [24], corn [21], barley [25] and cabbage [26].…”

Transgenic Indian Cotton (Gossypium hirsutum) Harboring Rice Chitinase Gene (Chi II) Confers Resistance to Two Fungal Pathogens

“…Transgenic cotton expressing the chloroperoxide or D4E1 genes showed antifungal activity against Aspergillus flavus and Verticillium dahliae [39] . The expression of 14-kDa Corn trypsin inhibitor gene was also showed resistance to A. flavus [40] . Similar to the above attempt, transgenic cotton plants harboring Talaromyces flavus GO gene results notable resistance against root pathogen Verticillium dahliae [41] .…”

Development of Maize Host Resistance to Aflatoxigenic Fungi

“…The mode of action of TI against fungal growth may be partially due to its inhibition of fungal -amylase, limiting A. flavus access to simple sugars [44] required not only for fungal growth, but also for toxin production [45]. TI also demonstrated antifungal activity against other mycotoxigenic species [46].…”