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ARS Home » Midwest Area » Madison, Wisconsin » Cereal Crops Research » Research » Publications at this Location » Publication #99166
Title: PRODUCTION OF PROTEASES BY FUSARIUM SPECIES GROWN ON BARLEY GRAINS AND IN MEDIA CONTAINING CEREAL PROTEINS

Author
item PEKKARINEN, A - VTT, FINLAND
item MANNONEN, L - VTT, FINLAND
item NIKU-PAAVOLA, M-L - VTT, FINLAND
item Jones, Berne

Submitted to: Journal of the American Society of Brewing Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Several species of fungi, called Fusarium, infect plants, including barley. These fungi have recently caused serious crop losses and destroyed the quality of barley and wheat crops grown in the US. Many of the Fusarium species produce toxic compounds that make the crops unsuitable for either humans or animals to use. They also render the barley unfit for making into malt. It seems likely that these fungi must make enzymes that can poke holes in the barley cells in order to get into the plant. One group of these enzymes, called proteases, would digest proteins. If those enzymes can be inactivated, this might make it impossible for the Fusarium to get into and degrade the plants. We are testing whether the fungi do make proteases and, if so, how those enzymes work. When three kinds of Fusarium were grown on barley cells, all made proteases and excreted them from their cells. However, the enzymes made by the different species were not all identical. Some of the enzymes worked at low pH values, some at high, but overall they worked best at pH 9. When grown in a solution that contained no barley cells they made no enzymes. The enzymes generally behaved like the well-studied mammalian enzyme called chymotrypsin. These enzymes will be characterized further and, after we define exactly how they work, it may be possible to inactivate the proteases of Fusarium cells that attack barley plants in the field. This might enable the barleys to resist attack by the fungi.

Technical Abstract: The production of proteases by the cereal plant pathogens Fusarium culmorum, F. graminearum and F. poae was followed through seven days of cultivation. The fungi were grown in mineral and in gluten culture media, and on autoclaved barley grains. The proteolytic activities of each sample were analyzed at pH 2.2, 5.0 and 8.0 and the pH optima of the most active proteases were determined. All of the fungi grown in the gluten medium produced proteases that were active at pH levels between 6.0 and 10.5 and were most active at pH 9.0. F. poae also produced acid protease(s) with pH optima between 3.0 and 3.5 when grown in the gluten medium. No protease activity was detected in the cultures that were grown in the mineral medium. When grown on the barley grain medium the Fusaria produced protease activities that were similar to the neutral and alkaline ones present in the gluten cultures, but no pH 2.2 protease activity was detected. The alkaline proteases had characteristics similar to those of chymotrypsin.