DEVELOPING BIOCONVERSION PROCESSES FOR HIGH-VALUE CARBOHYDRATE PRODUCTS
Location: Renewable Product Technology Research Unit
Title: Endo-B-1,4-xylanase inhibitors in shoots of germinating maize
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 12, 2007
Publication Date: September 12, 2007
Citation: Biely, P., Leathers, T.D., Cziszarova, M., Vrsanska, M., Cotta, M.A. 2007. Endo-B-1,4-xylanase inhibitors in shoots of germinating maize [abstract]. Annual Workshop of the Biotechnical Functionalistation of Renewable Polymeric Materials of COST. Abstract #O, p. 1.4.
Extracts of shoots of germinating maize, both leafs and roots, were found to contain endo-beta-1,4-xylanase (EX) inhibitors which were previously detected only in the maize meal (Goesaert et al., BBA 1696, 193-202, 2004). The inhibitors seem to be of the XIP type since they inhibit EXs of families 10 and 11 and also show some other characteristics compatible with the XIP inhibitors described in other cereals. They do not inhibit barley EX10, thus their physiological role could be the defense against phytopathogenic microorganisms. The XIP-I in maize is in fact induced by pathogens and wounding (Chivasa et al., Proteomics 5, 4894-4904, 2005). Size exclusion chromatography of a fraction of EX inhibitors isolated by cation-exchange chromatography afforded two types of EX inhibitors differing in size (30 kDa vs.10-15 kDa). The 30 kDa fraction denaturated on heating at 100 deg C at pH values 4 and higher, while the low Mw inhibitors showed unusual thermostability. In contrast to the thaumatin-like EX inhibitor from wheat inhibiting EXs11 (Fierens et al., Biochem. J. 403, 583-591, 2007), the maize low mol mass EX inhibitor affected mainly fungal EXs10. The effect on EXs11 was much weaker. A novel property of the low Mw EX inhibitor found in the shoots of germinating maize is its unusual thermostability at physiological pH values. The thermostability decreases with increase of pH of the heated solution. This property could be important for isolation of these inhibitors and could also have biotechnological significance for processes where EX activity should be eliminated.