Pectin methyl esterases

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. 

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. 

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. 

Each enzyme has one—and some enzymes have more—optimum pH values. For most enzymes this is in the range of 4.5 to 8.0. Examples of pH optima are amylase, 4.8 invertase, 5.0 and pancreatic a-amylase, 6.9. The pH optimum is usually quite narrow, although some enzymes have a broader optimum range for example, pectin methyl-esterase has a range of 6.5 to 8.0. Some enzymes have a pH optimum at very high or very low values, such as pepsin at 1.8 and arginase at 10.0. 

The occurrence of unwanted side activities in commercial pectinase preparations has been reported, and represents one of the main problems associated with their use in winemaking. Notably, increased formation of methanol during fermentation has been observed in association with pectinase treatment of the juice, due to pectin-methyl esterase activity (Revilla and Gonzdlez-SanJose 1998). Cinnamyl esterase... 

Pectinesterase action was first reported in 1840 by Fremy (56). He noted that the addition of carrot juice to a pectin solution caused formation of a gel. This gel was produced by the enzymatic deesterification of pectin followed by precipitation of the resulting polygalacturonic acid as calcium pectate 20), Various names such as pectin meth-oxylase and pectin methyl esterase have been applied to the enzyme, but pectinesterase is the preferred trivial name (57). 

In strawberry puree, pressurization above 250 MPa generated a poly-phenoloxidase activity loss of 60%, while peroxidase activity decreased in 25% with pressures above 230 MPa. A combination of temperature and pressure reduced the activity of pectin methyl esterase in orange juice by up to 50% (Cano et al., 1997). As shovm by Basak and Ramaswamy (1996), the inactivation of pectin methyl esterase in orange juice depends on pressure level, time of treatment, pH, and soluble solids content. In Satsuma mandarin juice, 300-400 MPa for 10 min was required to partially inactivate the pectin methyl esterase, which was reactivated neither after treatment nor during storage. This demonstrated that the greater the concentration of soluble solids in the medium the lower the inactivation of the enzyme (Ogawa et al., 1990). 

Pectin methyl esterase in juices requires processing times of 10 min combined with pressures of 600 and 1000 MPa and temperatures of 57 and 20°C, respectively. These combinations prevent microbial deterioration, but must be combined with a mild blanching, refrigerated storage and addition of inhibitory enzymes to achieve a stable product with respect to pectin methyl esterase (Cheftel, 1992). Guava puree samples were treated with pressures of 400 and 600 MPa looking for pectinesterase and pol)q)henoloxidase inactivation. The residual activity of the former was greater than 76%, while of the latter was above 63% at the lower pressure. 

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