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United States Department of Agriculture

Agricultural Research Service

Title: Uronate Methyl Esters and Benzyl-Uronate Cross-Links Restrict the Enzymatic Hydrolysis of Pectin in Cell Walls

Authors
item Grabber, John
item Hatfield, Ronald
item Ralph, John

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: November 9, 2000
Publication Date: N/A

Technical Abstract: Nonlignified (NL) walls from cell suspensions of Zea mays (L.) were treated with pectin methylesterase (PME) and then synthetically lignified (SL) with coniferyl alcohol to assess whether uronate methyl esters and benzyl-uronate cross-links restrict pectin and cell wall degradation by fungal enzymes. PME treatment of walls reduced uronic acid concentrations from 110 to 90 g/kg and methyl esterification of uronic acids from 51 to 20%. Klason lignin concentrations in SL walls were, however, increased from 99 to 116 g/kg by PME treatment. The release of uronic acids after 4- and 72-h of enzymatic hydrolysis were 58 and 76% for NL walls, 68 and 94% for PME-NL walls, 44 and 79% for SL walls and 23 and 86% for PME-SL walls, respectively. These results indicate that methyl esters restrict both the rate and extent of pectin degradation. Demethylation of uronic acids, however, enhanced the formation of benzyl-uronate cross-links in SL walls and these cross-links limited the rate but not the extent of pectin degradation. Lignification reduced the release of total sugars from 468 to 144 g/kg after 4 h and from 771 to 510 g/kg after 72 h of enzymatic hydrolysis. Pectin methylation and benzyl-uronate cross-linking did not influence the release of total sugars from NL or SL walls during enzymatic hydrolysis.

Last Modified: 10/22/2014
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