Punahometta aiheuttavan Fusarium-sienen seriiniproteinaasit ja niiden inhibiittorit

Fusarium head blight (FHB, scab) of cereals is a serious, world-wide problem for producers and industries that use grain as raw material. Scabby grain processes poorly and the toxins that are produced by the fungi pose potential health risks to humans and animals. Understanding the interactions between the fungus and the plant would help in developing more resistant cereal cultivars that also have good agronomical and malting qualities. Proteolytic enzymes may be among the tools that the fungus use to attack the spikes. The purpose of this dissertation was to pinpoint and characterize the proteinases that are synthesized by Fusarium species to degrade grain proteins during infection and to identify any barley proteins that can inhibit those enzymes. The proteinases, a subtilisin-like (SL) and a trypsin-like (TL) enzyme, were shown to degrade barley storage proteins, C and D group hordeins. This implied that they are involved in increasing free amino nitrogen (FAN) and soluble protein levels in malt. The grain proteins that inhibited the SL enzyme were barley alfa-amylase/subtilisin inhibitor (BASI) and chymotrypsin/subtilisin inhibitors 1A, 1B and 2A. The TL enzyme was inhibited by barley Bowman-Birk inhibitor (BBBI). The roles that these proteinases and their inhibitors may play during the infection of cereal spikes by Fusaria were discussed in the dissertation, but more research is needed to establish their true purposes.