Alpha-(4-O-methyl)-D-glucuronidase activity produced by the rumen anaerobic fungus Piromonas communis: a study of selected properties.
The rumen anaerobic fungus Piromonas communis, unlike the rumen anaerobic fungi Neocallimastix frontalis and Neocallimastix patriciarum, produced extracellular alpha-(4-O-methyl)-D-glucuronidase when grown in cultures containing filter-paper, barley straw, birchwood xylan or birchwood sawdust as carbon source. The highest concentration of enzyme was produced in cultures containing birchwood sawdust. The aldobiouronic acid O-alpha-(4-O-methyl-D-glucopyranosyluronic acid)-(1-->2)-D-xylopyranose (MeGlcAXyl) was the best substrate of those tested: the aldotriouronic acid O-alpha-(4-O-methyl-D-glucopyranosyluronic acid (1-->2)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose (MeGlcAXyl2) and the aldotetraouronic acid O-alpha-(4-O-methyl-D-glucopyranosyluronic acid)-(1-->2)-O-beta-D- xylopyranosyl-(1-->4)-O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose (MeGlcAXyl3) were also attacked but the rate fell as the degree of polymerisation increased. When the same substituted xylo-oligosaccharides were reduced to the corresponding alditols the enzyme activity disappeared. Similarly, p-nitrophenyl-alpha-D-glucuronide was not a substrate. Remarkably, the relative rates of attack shown by the alpha-(4-O-methyl)-D-glucuronidase on the aldouronic acids and on xylans extracted from birchwood, oat spelts and oat straw differed according to the carbon source used to produce the enzyme. The alpha-(4-O-methyl)-D-glucuronidase had a pH optimum of 5.5 and a temperature optimum of 50 degrees C. On gel filtration the enzyme was shown to be associated with proteins covering the range 100-300 kDa, but a major peak of activity in the column effluent appeared to have a molecular mass of 103 kDa.
Wood
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TM
Rowett Research Institute, Bucksburn, Aberdeen, UK.
Wilson
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CA
D000693:Anaerobiosis; D000818:Animals; D002240:Carbohydrate Sequence; D008411:Chytridiomycota / Q000201:enzymology*; D004795:Enzyme Stability; D005966:Glucuronidase / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009844:Oligosaccharides / Q000378:metabolism; D012417:Rumen / Q000382:microbiology; D012756:Sheep; D013379:Substrate Specificity; D013696:Temperature; D014934:Wood; D014990:Xylans / Q000378:metabolism
D009844:Oligosaccharides; D014990:Xylans; D005966:Glucuronidase