The membrane-bound alpha-glucuronidase from Pseudomonas cellulosa hydrolyzes 4-O-methyl-D-glucuronoxylooligosaccharides but not 4-O-methyl-D-glucuronoxylan.
The microbial degradation of xylan is a key biological process. Hardwood 4-O-methyl-D-glucuronoxylans are extensively decorated with 4-O-methyl-D-glucuronic acid, which is cleaved from the polysaccharides by alpha-glucuronidases. In this report we describe the primary structures of the alpha-glucuronidase from Cellvibrio mixtus (C. mixtus GlcA67A) and the alpha-glucuronidase from Pseudomonas cellulosa (P. cellulosa GlcA67A) and characterize P. cellulosa GlcA67A. The primary structures of C. mixtus GlcA67A and P. cellulosa GlcA67A, which are 76% identical, exhibit similarities with alpha-glucuronidases in glycoside hydrolase family 67. The membrane-associated pseudomonad alpha-glucuronidase released 4-O-methyl-D-glucuronic acid from 4-O-methyl-D-glucuronoxylooligosaccharides but not from 4-O-methyl-D-glucuronoxylan. We propose that the role of the glucuronidase, in combination with cell-associated xylanases, is to hydrolyze decorated xylooligosaccharides, generated by extracellular hemicellulases, to xylose and 4-O-methyl-D-glucuronic acid, enabling the pseudomonad to preferentially utilize the sugars derived from these polymers.
Nagy
Tibor
T
Department of Biological and Nutritional Sciences, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, United Kingdom.
Emami
Kaveh
K
Fontes
Carlos M G A
CM
Ferreira
Luis M A
LM
Humphry
David R
DR
Gilbert
Harry J
HJ
D001483:Base Sequence; D020633:Cellvibrio / Q000201:enzymology; D006026:Glycoside Hydrolases / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D006868:Hydrolysis; D008565:Membrane Proteins / Q000502:physiology; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology*; D012336:RNA, Ribosomal, 16S / Q000737:chemistry; D014990:Xylans / Q000378:metabolism*
D008565:Membrane Proteins; D009844:Oligosaccharides; D012336:RNA, Ribosomal, 16S; D014990:Xylans; C044967:4-O-methyl glucuronoxylan; D006026:Glycoside Hydrolases; C096734:alpha-glucuronidase