Pectinolytic enzyme

Pectins (cf. 4.4.4.13) in plant foods are attacked by a series of enzymes. A distinction is made between  

The second group can be further subdivided according to the substrate (pectin or pectic acid) and to the site of attack (endo-/exo-enzyme), as shown in Table 4.28. The endo-enzymes strongly depolymerize and rapidly reduce the viscosity of a pectin solution. 

Polygalacturonases occur in plants and microorganisms. They are activated by NaCl and some by Ca ions as well. 

Pectin and pectate lyases are only produced by microorganisms. They are activated by Ca ions and differ in the pH optimum (pH 8.5-9.5) from the polygalacturonases (pH 5-6.5). 

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The permeability of the films to paracetamol as a model compound was dependent on film composition and was markedly increased after exposure to pectinolytic enzymes, used to mimic conditions in the colon. Similar formulations, apphed as a film coat to tablets, were used with colonic conditions for an increased release rate [242],... 

The influence of enzyme maceration using pectinolytic enzyme preparations (Pectofruit and Pectofruit Press) on anthocyanin extraction at 43°C from two variants of black currant berries was studied. Enzymes accelerated the extraction yield the yield of anthocyanin extraction was similar for both enzymes and the duration did not influence the total content of released pigments. 

Optimizing pectinolytic enzyme expression Promoter gene fusions... 

The use of A. niger prtF for expression, the strong glycolytic pkih promoter to drive transcription under carbon and nitrogen repressing conditions and the use of high phosphate buffered media ensures a sufficient yield of individual pectinolytic enzymes. 

Among the five different species of Azospirillurn, only A. irakeme shows clearly pectinolytic activity on solid and in liquid medium. Moreover, this species can grow under non-diazotrophic as well as diazotrophic conditions when pectin is the sole carbon source (Khammas and Kaiser, 1991). Khammas and Kaiser (1991) analysed the pectinolytic activity of seven A. irakense isolates, and gave evidence for the presence of two types of pectinolytic enzymes. All strains tested have inducible Ca dependent pectate lyase activity. Six strains, showed also pectin methylesterase activity. So far, none of the corresponding enzymes have been purified. 

In order to characterize the pectinolytic enzymes encoded by these clones, the culture supernatants of all these clones were tested for pectate lyase and polygalacturonase activity, using thiobarbutiric acid as described in materials and methods. Absorption at 550 nm indicates the activity of pectate lyase whereas absorption at 510 nm indicates the activity of polygalacturonase. 

In A. irakense most of the pectinolytic activity is found in the culture supernatant. In the E. coli transconjugants, the pectinolytic enzymes need to be released by cell... 

In some cases pectinolytic enzymes have been associated with virulence and it is generally accepted that pectinolysis by these bacteria facilitates their entry and spread in plant tissue. In Rhizohium, these enzymes may play a role in the root infection process that precedes nodule formation (Hubbell et al 1978). A. irakense has never been reported to be pathogenic on plants. It can therefore be speculated that moderate and strictly regulated pectinolysis of A. irakense facilitates entry in the outer cortex of plants roots, since A. irakense has been isolated from surface-sterilized roots. It is likely that breakdown of plant polysaccharides by root colonizing bacteria can provide them with extra carbon source. 

Hubbell, D.H., Morales, V.M and Umali-Garcia, M., 1978. Pectinolytic enzymes in Rhizobium. Appl, Environ. Microbiol. 35, 210-213. 

Mateos, P.F., Jimener-Zurdo, J.I., Chen, J., Squartini, A S., Haack, S.K., Martinez-Molina, E., Hubbell, D.H. and Dazzo, F.B., 1992. Cell-associated pectinolytic enzymes in Rhizobium leguminosarum biovar trifoUi. Appl. Environm. Microbiol. 58, 1816-1822... 

The solubilisation of soy cell wall material (CWM) by the two rhamnogalacturonases (RGase A and RGase B) in combination with other pectinolytic enzymes were compared in order to identify enzymes for new soy processes or products. The experiments were carried out at pH 5.0, where both rhamnogalacturonases have about 25% of their maximum activity, and with high enzyme dosages to ensure that the maximum effects are obtained. 

The composition of the resulting soy product is shown on Table V, where it is seen that the protein content was unchanged, whereas raffinose, stachyose and phytate were almost removed, and the amount of dietary fibres was improved. This demonstrates that the availability of relatively pure pectinolytic enzymes, like the used RGase B, opens up for the new types of soy processes and products. 

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. 

For pectinolytic enzymes no glycosyl transfer reaction have been reported except for D-galacturonan digalacturonohydrolase (EC 3.2.1.82) from Selenotnonas ruminantium [4]... 

Strains deleted for the pel genes have been constructed from different E. chrysanthemi strains (5, 7, 8). These strains are still able to macerate plant tissues, suggesting the existence of additional pectinolytic enzymes, so called "secondary pectinases". Similarly, a pemA mutant has a reduced virulence but still remains able to cause local necrosis on Saintpaulia (9). Thus, other enzymes with PME activity could exist in E. chrysanthemi. 

Up to now, the pectinolytic enzymes of E. chrysanthemi that have been detected were extracellular secreted enzymes (PelA, B, C, D, E, L, exo-Peh and PemA), periplasmic (exo-Pel), or cytoplasmic (OGL) proteins (1, 5). In contrast, PemB is an outer membrane pectinolytic enzyme. To our knowledge it is the first pectinase characterised as a membrane protein. We presented several lines of evidence showing that PemB is a lipoprotein (i) Its N-terminal sequence has the characteristics of lipoprotein signal sequences, (ii) PemB is synthesised as a high molecular weight precursor processed into a lower molecular weight mature form, (iii) Palmitate, the most prevalent fatty acid in bacterial lipoproteins (12), is incorporated into PemB. 

Pectinolytic enzymes secreted by the diploid K. marxianus have been partially purified and characterized [eg 2] but the results obtained were very variable, partially contradictory and paid little attention to the physiological aspects of PG secretion [3]. Commercial use and production of PG from K. marxianus has attracted considerable interest [4]. 

Soft rot symptoms produced by E. chrysanthemi consist of a disorganisation of parenchymatous tissues following the release of bacterial pectinolytic enzymes. The diverse enzymes do not contribute equally to the virulence on a given host and their implication may vary according to the host considered. For instance, inactivation of pelE, pelD, pelA or pern in strain 3937 considerably reduces the virulence on African violets while mutations in pelB or pelC remain ineffective [2]. Pectinolysis is regulated by the transcriptional repressor KdgR, inactive in the presence of pectic inducers. 

Regarding the prevalence of pectinolytic enzymes in the soft rot symptoms, it is noteworthy that the experimental model developed on African violets stresses the dynamic aspect of the disease and illustrates a number of points which have long been questioned. 

Cloning, sequence and expression of the gene coding for rhamnogalacturonase (RHG) of Aspergillus aculeatus a novel pectinolytic enzyme... 

Suykerbuyk MEG, Schaap PJ, Stam H, Musters W, Visser J (1995) Cloning, sequence and expression of the gene coding for rhamnogalacturonase (RHG) of Aspergillus aculeatus-, a novel pectinolytic enzyme. Appl Microbiol Biotechnol 43 861-870... 

Pretreatment of wood with pectinolytic enzymes facilitates the debarking. The energy consumption during debarking of spruce in a laboratory scale debarker is clearly decreased after treatment with Pectinex Ultra (Table 1). Several hours is needed for effective preteatment (Table 2). 

E. Martino, J. D. Coi.sson, I. Lacourt, F. Favaron, P. Bonfante, and S. Perotto, Influence of heavy metals on production and activity of pectinolytic enzymes in ericoid mycorrhizal fungi. Mycol Res. In press. 

Cellulolytic and pectinolytic enzymes used to reduce the amount of sulphuric acid required. 

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