Chitinases of wheat seedling and their biochemical properties

Chitinases are important protective enzymes in plants and belong to a special group of pathogenesis-related (PR) proteins. The main target of these enzymes is various pathogenic fungi that contain chitin in their cell walls. Under the influence of fungi, chitinases produced by plants, hydrolyze chitin, which leads to suppression of the growth and death of the pathogen. Considering their important protective role, much attention is paid to the studies of these enzymes. Individual isozymes of chitinase are often used in testing and breeding agricultural plants for resistance to fungal diseases. In this work, we studied the isoenzyme composition and a number of physicochemical properties of wheat chitinases, which are important for a better understanding of their functioning in this grain crop. It was found that in seedlings of 7 days old, chitinases are localized both inside and outside the cells. Intracellular chitinase is represented only by basic components, whereas extracellular – by acidic ones. Using an affinity sorbent, the forms of the enzyme with a chitin-binding domain (CBD) were determined, which had isoelectric points (pI) of 9.3, 9.0, 8.6, 8.2, 8.0, 7.6, 5.7 and 4.6. According to SDS-PAG electrophoresis, the molecular weight (M.w.) of these enzymes corresponded to the values of 33, 35 and 56 kDa and they were not the glycoproteins. In the spectrum of isoelectric focusing (IEF) of chitinases, exochitinases were identified, which had pI values exclusively in the acidic range of 4.3-5.2. Significant differences were revealed in the thermal stability of chitinases. The acidic components were most resistant to elevated temperatures.