Pectin esterase

Immobilization. The fixing property of PEIs has previously been discussed. Another appHcation of this property is enzyme immobilization (419). Enzymes can be bound by reactive compounds, eg, isothiocyanate (420) to the PEI skeleton, or immobilized on soHd supports, eg, cotton by adhesion with the aid of PEIs. In every case, fixing considerably simplifies the performance of enzyme-catalyzed reactions, thus faciHtating preparative work. This technique has been appHed to glutaraldehyde-sensitive enzymes (421), a-glucose transferase (422), and pectin lyase, pectin esterase, and endopolygalacturonase (423). 

Hall, L. N., Bird, C. R., Picton,S. P., Tucker, G. A., Seymour, G. B and Grierson, D (1994) Molecular characterisation of cDNA clones representing pectin esterase isozymes from tomato. Plant Molecular Biology. 25. 313-318. 

Pectin esterase activity was assayed by measuring the decreasing of pH in the reaction mixture which equal to methanol liberated by the method of Wood, et al. (11). 

The catalytic capacity of several excreting pectolytic enzymes obtained from various yeast strains was examined using in vivo and biochemical techniques. Of the 33 yeast strains studied 30 were isolated from champagne wine during alcoholic fermentation. Only one yeast strain was found to excrete pectolytic enzymes and was identified as Saccharomyces cerevisiae designated SCPP. Three types of pectolytic enzymes were found to be excreted by SCPP polygalacturonase (PG), pectin-lyase (PL) and pectin-esterase (PE) [1]. 

The pathogenicity of Erwinia chrysanthemi 3937 on African violets involves at least five pectate lyases (PelA to PelE), one methyl pectin esterase (Pern), encoded by pelA to pelE, pern genes and an iron assimilation system mediated by chiysobactin [1], (Fig. 1). 

The strains were cultured on Mandels medium + 1% citrus pectin for 5 days and the enzymatic activities of culture filtrates were determined on three substrates citrus pectin, polygalacturonic acid and filter paper, (a) extracellular proteins are in p.g/ml. (b) p>ectinolytic activities on pectin (PC) and on polygalacturonic acid (TO) and Pectin esterase (PE) are in units/ml. (c) total cellulolytic activity (filter paper, fp) are in mg of liberated reducing sugars/ml. 

The interaction of Ca2+ with pectins is discussed. The role of carboxylic acid salt formation and the degree of polymerization are first considered in terms of electrostatic and/or cooperative specific interactions. Then the effect of the degree of esterification and that of the pattern of carboxylic group distribution are discussed pectin esterase forms blocks which behave as fully hydrolyzed polymers and favor aggregation. Finally, the role of the calcium addition on the degree of aggregation was established. All the data show the important role of molecular structure of the pectins on calcium interactions. 

Ray, J., Knapp, J., Grierson, D., Bird, C. Schuch, W. (1988). Identification and sequence determination of a cDNA clone for tomato pectin esterase. European Journal of Biochemistry 174, 119-24. 

Pectic enzymes are defined and classified on the basis of their action toward the galacturonan part of the pectins. Two main groups are distinguished pectin methylesterases (pectin esterase, PE EC 3.1.11.1), which split off methoxy groups from pectin, transforming... 

Table I. Occurrence of pectin esterase and polygalacturonase in higher plants (23,26,35,45)...

Endogenous pectin esterases play an important role in citrus processing they have therefore been studied intensively. They cause cloud loss in citrus juices, which is due to the calcium precipitation of enzymatically de-esterified pectin. This is desirable in the production of lemon and lime juices but undesirable in the production of orange juice. In orange juice concentrates strong calcium pectate gels may form which cannot be reconstituted... 

Versteeg et al. (50) have isolated various multiple forms of pectin esterases in oranges and shown that they differ in affinity to pectins and pectates and in heat stability and therefore may play different roles in cloud loss phenomena. One form (about 5% of the total PE activity) was found to be much more heat stable than the other forms it was also active at low pH (2.5) and at low temperatures. Another form did not cause self-clarification for this enzyme a similar mode of attack was proposed as for fungal pectin esterases which produce low-ester pectins less sensitive to calcium. Multiple forms of pectin esterases are present in the fruits of all of the orange varieties and citrus species tested. The two isoenzymes known to be responsible for cloud loss and gelation in citrus products were found to occur in all of the component parts of the orange fruit (51). In the French cider industry the endogenous PE of apple is used for the self-clarification of apple juice (52). 

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