title: Unprocessed barley aleurone endo-beta-1,4-xylanase X-I is an active enzyme.
abstract: Endo-beta-1,4-xylanase X-I is a major hydrolase produced by the aleurone tissue of germinating barley grain. It was previously reported that this cytosolic enzyme is synthesized as an inactive precursor which is proteolytically processed to active forms upon its programmed cell death dependent release. We here demonstrate, however, that the precursor form of X-I is an active enzyme. Purified recombinant precursor X-I was characterised with respect to its molecular weight, iso-electric point and temperature and pH activity and stability. Analysis of the hydrolysis products showed that it is an endo-acting enzyme which has the striking ability to release xylose from both polymeric xylan as well as from small xylo-oligosaccharides. The implications of these findings in relation to the putative role of the N-terminal propeptide as a carbohydrate binding module and the possible consequences for the way X-I fulfils its role in the germination process, are discussed.
authors: Laboratory of Gene Technology, K.U. Leuven, Kasteelpark Arenberg 21, B-3001 Leuven, Belgium. steven.vancampenhout@biw.kuleuven.be
authors: Steven
authors: S
authors: Van Campenhout
authors: Annick
authors: A
authors: Pollet
authors: Tine M
authors: TM
authors: Bourgois
authors: Sigrid
authors: S
authors: Rombouts
authors: Johnny
authors: J
authors: Beaugrand
authors: Kurt
authors: K
authors: Gebruers
authors: Evelien
authors: E
authors: De Backer
authors: Christophe M
authors: CM
authors: Courtin
authors: Jan A
authors: JA
authors: Delcour
authors: Guido
authors: G
authors: Volckaert
mesh_terms: D003001:Cloning, Molecular; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry / Q000378:metabolism*; D004795:Enzyme Stability; D004926:Escherichia coli / Q000378:metabolism; D018525:Germination / Q000502:physiology; D001467:Hordeum / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D008970:Molecular Weight; D013696:Temperature; D014990:Xylans / Q000378:metabolism
chemical_list: D014990:Xylans; D043364:Endo-1,4-beta Xylanases