Affiliation:
1. Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, Jaime Roig 11, 46010 Valencia, Spain
Abstract
By applying different classical and fast protein liquid chromatographic techniques, three xylanases (β-1,4-
d
-xylan xylanhydrolase) were purified to homogeneity from the extracellular enzymatic complex of
Bacillus polymyxa
. The three enzymes (X
34
C, X
34
E, and X
22
) were small proteins of 34, 34, and 22 kDa and basic pIs 9.3, >9.3, and 9.0, respectively. X
34
C and X
34
E are closely related and seem to be isoforms of the same enzyme. However, they differ in some characteristics. The three enzymes had different pH and temperature optima. One of them, X
34
E, showed a high thermal stability. The
V
max
values determined for X
34
C, X
34
E, and X
22
enzymes on oat spelts xylan were 14.9, 85.5, and 64.0 U mg
-1
, respectively, and 16.1, 62.0, and 150.6 U mg
-1
on birchwood xylan. When oat spelts xylan was the substrate used,
K
m
values of 3.4, 2.4, and 1.9 mg ml
-1
were obtained for X
34
C, X
34
E, and X
22
enzymes, respectively, and 0.65, 6.3, and 0.32 mg ml
-1
were the respective
K
m
values determined with birchwood xylan as the substrate. The enzymes were nondebranching endo-β-xylanases. Xylose was one of the products of xylan hydrolysis by xylanases X
34
C and X
34
E, but this monosaccharide was not released by X
22
enzyme. However, neither of the enzymes was able to degrade xylobiose.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology