Pectin degradation and

PG and pectin degradation during tomato fruit ripening... 

In this report we describe the kinetics of pectate and pectin degradation by Eca PL isoenzymes. Moreover, action pattern analyses using various pectic substances provide further insights into specific differences among the isoenzymes. 

Action pattern analyses of pectin degradation. HPAEC data of oligomers released from 68% esterified pectin by combinations of Eca PLs are graphically represented. Arrows indicate addition of the third enzyme. Products with degrees of polymerization ranging from 2 to 9 were detected. The graphs illustrate the generation of dimers (A), trimers ( ) and pentamers ( ). 

Since the first steps of pectin degradation are extracellular, the intracellular catabolism is dependent on the permeabihty of the membrane to the external substrates. Oligogalacturonides can enter the cells but the corresponding transport system(s) have not yet been identified (14). Two transport systems which mediates entry of monomers were characterised ExuT for galacturonate uptake (35) and KdgT for DKI, DKIl or KDG uptake (36) (Figure 1). 

Molecular genetic and biochemical aspects of pectin degradation in Aspergillus... 

Tucker,G.A.,Seymour,G.B.,Bundick,Y.,Robertson,D.,Sniith,C.J.S and Grierson,D (1992) Use of antisense RNA technology to manipulate pectin degradation in tomato fiuit. New Zealand Journal of Horticultural Crop Botany. 20.119-124... 

Watson,C.F., Zheng,L.S and Delkpetma,D (1994) Reduction of polygalacturonase beta-subunit expression affects pectin solubilisation and degradation during fiuit ripening. Plant Cell. 6. 1623-1643. 

The plant cell wall is a polymeric mesh consisting of cellulose, hemicellulose, pectin and protein. Cellulose and hemicellulose are integral components of the cell wall, but pectic substances are located mainly in the outer wall regions within the middle lamella (McNeil et ai, 1984). Pectic substances are more susceptible to enzymatic degradation, because they are more exposed than other cell wall components. Therefore, pectin-degrading enzymes may play a central role in the penetration of plant tissue by bacteria. 

If we compare liquefaction to maceration, more activities are needed to liquefy the cell wall. Since 1991, new pectinases activities such as rhamnogalacturonase, pectin acetylesterase and xyloglucanases complex have been found to be important in the apple liquefaction by Henck Schols, Jean-Paul Vincken and Voragen [3]. The cellulose-xyloglucan complex accounts approximatively 57% of the apple cell-wall matrix. In a liquefaction process, an efficient enzymic degradation of this complex is crucial to increase the sugars extraction, to decrease the viscosity of the pulp then to be able to ultra-filtrate the juice without second depectinisation, at last to have negative alcohol tests required by some concentrate customers. 

Pectin degradation requires fee combined action of various enzymatic activities. However, evaluation of fee contribution of individual pectinases in Suit juice extraction and clarification is rather complicated. Most commercial pectinolytic enzyme preparations are produced by fermentation wife filamentous fungi, mostly strains belonging to fee genus Aspergillus,. plication studies with mixtures of isolat enzymes obtained by fermentation or by means of fractionation of commercial enzyme preparations can be used to assess the importance of fee various individual enzymes. Subsequently, molecular biology and fermentation technology can be used to enhance specific desirable enzymatic activities. 

Neukom H. Deuel H. (1958) Alkaline degradation of pectins. Chemistry and Industry June 1958, 683. 

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