New enzymes active towards pectic structures

被引：8

作者：

Beldman, G

Mutter, M

SearlevanLeeuwen, MJF

vandenBroek, LAM

Schols, HA

Voragen, AGJ

机构：

[1] Wageningen Agricultural University, Department of Food Science, 6703 HD Wageningen

来源：

PECTINS AND PECTINASES | 1996年 / 14卷

关键词：

D O I：

10.1016/S0921-0423(96)80258-9

中图分类号：

Q81 [生物工程学（生物技术）]; Q93 [微生物学];

学科分类号：

071005 ; 0836 ; 090102 ; 100705 ;

摘要：

Microbial pectinases have been used for fruit and vegetable processing for already more than half a decade. With respect to application as well as to fundamental research, most attention has been paid to those enzymes acting towards the 'smooth' homogalacturonan part of the pectin molecule (i.e. polygalacturonase, pectin lyase, pectate lyase, pectin methyl esterase). More recently, enzymes active towards the 'hairy' rhamnogalacturonan part of pectin gained attention, since it was found that in juice processing those structures foul the ultrafiltration membranes used in a final clarification step. Two different rhamnogalacturonases (RGases A and B) were identified and purified from an Aspergillus aculeatus preparation, using apple pectic hairy regions (MHR) as substrate. Based on the structure of the products, RGase A was identified as a hydrolase, splitting the alpha-GalA(p)-(1-2)-alpha-Rha(p) linkage in rhamnogalacturonan, while RGase B appeared to be a lyase splitting the alpha-Rha(p) alpha-(1-4)-GalA(p) linkage by beta-elimination. Rhamnogalacturonan oligosaccharides were used to identify and purify two other novel enzymes with high specificity towards rhamnogalacturonan fragments: a rhamnogalacturonan rhamnohydrolase acid a rhamnogalacturonan galacturonohydrolase. As an accessory enzyme for the RGases, rhamnogalacturonan acetyl esterase (RGAE) was discovered in the same A. aculeatus preparation. This enzyme appeared to be specific for the de-acetylation of MHR and essential for the degradation of MHR by RGases A and B. The same enzyme (RGAE) could be purified from A. niger, together with two other esterases: a feruloyl esterase (FAE) and an acetyl esterase (PAE) specific for the removal of one type of acetyl group present in the 'smooth' regions of sugar-beet pectin. Finally, the A. aculeatus preparation was found to contain an enzyme releasing the dimer beta-Xyl(p)-(1-3)-GalA(p) from a soluble soy cell wall polysaccharide. The enzyme was partially purified and appeared to be active towards saponified MHR and gum tragacanth as well. It was concluded that this enzyme degraded the xylogalacturonan part in MHR by an exo-fashion.

引用

页码：231 / 245

页数：15

共 15 条

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