Pectins, methylation

Fig. 10. Intercellular junction zones of carrot cells grown in suspension have been observed in electron microscopy after immunogold labeling with the 2F4 antibody, (a) no treatment of the sections prior to labeling the gold particles are restricted to the center of the junction zones (b) enzymatic (pectin methyl esterase) deesterification of the E.M. grids before labeling the deesterified pectins present in the primary walls now bind the probe. Scale bars = 1 pm.

The chromatogram of the serum from juice with poor cloud stability obtained after mash treatment with the enzyme mixture including the pectin depolymerisation enzyme combination of polygalacturonase and pectin methyl esterase is seen to be lacking the A-peak. High molecular pectin is therefore considered to be a prerequisite for a cloud stable juice. 

Chamay, D. Nari, J. Noat, G. 1992. Regulation of plant cell-wall pectin methyl esterase by polyamines -Interactions with the effects of metal ions. Eur. J. Biochem. 205 711-714. 

Enzymes can be used to specifically modify the pectins. Pectin methyl esterase is already widely used to adjust the gelling properties of commercially available pectins. The acetyl esters also strongly affect the gelation [2,3] and removal is important for the upgrading of sugar beet pectin, extractable from a by-product of the sugar industry. 

This enzyme [EC 3.1.1.11] also known as pectin methyl-esterase, pectin demethoxylase, and pectin meth-oxylase, catalyzes the reaction of pectin with n water to produce pectate and n methanol. 

The prevailing concept is that, in the softening that accompanies ripening, textural changes occur as insoluble, wall-bound protopectin of high molecular weight, after partial de-esterification by pectin methyl... 

Schols and Voragen, 2002). Other substrates, such as citrus pectin, may be used in some cases, but overall PGase activities will probably be lower on the esterified pectins, and results from assays using the esterified pectins are more likely to be influenced by non-PGase enzymes, particularly pectin lyase and pectin methyl esterase (see Commentary). 

Wood, P.J. and Siddiqui, l.R. 1971. Determination of methanol and its application to the measurement of pectin ester content and pectin methyl esterase activity. Anal. Biochem. 39 418-428. 

A certain amount of evidence shows that methyl group metabolism may be affected as a result of auxin treatment—generally increased pectin-methyl esterification is observed (7). Though pectin-methyl esterification may be correlated with increased wall plasticity, there are as yet no obvious connections between general methyl group availability on the one hand and permeability, peroxidation, and mitosis on the other. 

Laratta et al.(15) studied five tomato varieties and all varieties showed the same thermal performance the thermal pectin methyl esterase resis-... 

Willats, W. G., Orfila, C., Limberg, G., Buchholt, H. C., van Alebeek, G. J., et al., Modulation of the degree and pattern of methyl-esterification of pectic homogalacturonan in plant cell walls. Implications for pectin methyl esterase action, matrix properties, and cell adhesion. J Biol Chem 2001, 276 (22), 19404-13. 

---