Pectinesterase forms

By means of gel electrophoresis on cross-linked, hydrolyzed starch,99 with simultaneous checking for proteins, lipids, and pectinesterase activity, it was found, however, that the product isolated after the separation on CM-Sephadex C-50 constitutes but one of five multiple forms of tomato pectinesterase, and is the one present in preponderant proportion98 (see Fig. 4). The accompanying lipid and sugar components were separated from this pectinesterase form in the course of the purification procedure. After analysis of the hydro-lyzate of the final product for fatty acids, as well as for carbohydrate components, it was possible to exclude the possibility of a lipoprotein,30 as well as glycoprotein,100 character of this form of tomato pectinesterase. 

Pressey,R and Avants,J.K (1972) Multiple forms of pectinesterases in tomatoes. Phytochemistry. 11. 3139-3142. 

Evans, R. McHale, D. 1968. Multiple forms of pectinesterase in limes and oranges. Phytochemistry 17 1073-1075. 

It was found out that reaction of the hydrolysis of highlymetoxilated beet pectin (catalyzed by P. fellutanum pectinesterase) obeyed Michaelis—Menten equation only under low substrate concentrations (up to 1.2%), when graph of the dependence of reaction speed was hyperbolic in form. 

Fig. 4. — Monitoring of the Multiple Molecular Forms of Tomato Pectinesterase by Starch-gel Electrophoresis.98 [ENZ, detection of pectinesterase activity by paper print with pectin and Bromothymol Blue PROT, protein staining with nigrosin O, origin. Key A, 1 crude tomato extract after ammonium sulfate salting-out, and dialysis 2 pectinesterase fraction from column of DEAE-Sephadex A-50 3 and 4 pectinesterase fractions from column of Sephadex G-75. B, Two parts of the same gel after horizontal slicing 1, 500 fig of the isolated form of pectinesterase from a column of CM-Seph-adex C-50 with 175 mM phosphate-sodium chloride buffer 2, active fraction at 150 mM buffer 4 and 5, 250 fig and 1 mg of the isolated form of pectinesterase, respectively.]...

Four forms of pectinesterase were found in different tomato varieties (Marion, Homestead, and Pixie)83 by separation on columns of DEAE-Sephadex A-50, using elution with 150 mM sodium chloride at pH 6.0. By gel filtration on columns of Sephadex G-100, the molecular weights of the individual forms were found to be 22,000-27,000, and 35,000. 

By use of starch-gel electrophoresis, the total extract of bananas, and the fractions obtained after separation on DEAE-Sephadex A-50, were found to contain six multiple forms of pectinesterase having electrophoretic patterns different from those of tomato pectinesterase.103... 

Among the microbial pectinesterases, the one from Coniothyrium diplodiella56 was purified by repeated chromatography on columns of Duolite A-2 and DEAE-cellulose. Two electrophoretically homogeneous forms of pectinesterase were obtained, having an identical pH optimum and the same behavior towards pectins of different d.e. 

The method was used in a modified form for the purification of endo-D-galacturonanase from tomatoes.212 Elution from the column by use of a linear pH gradient led to the separation of pectinesterase and of three multiple molecular forms of endo-D-galacturonanase dif-... 

Multiple forms of pectinesterase have been reported. Reid (64) separated two active pectinesterase fractions from a fungal source and suggested that pectinesterases from various organisms diflFer in their initial rates and final percent deesterification of pectin. Glasziou and Inglis (65) found two pectinesterases present in tobacco pith one of which was firmly bound to the cell walls. Hulton and Levine (66) observed three molecular forms of pectinesterase in the pulp of the... 

Pressey and Avants (80) separated, by DEAE Sephadex A-50 chromatography, four forms of tomato pectinesterase, with molecular weights 35,500, 27,000, 23,700, and 24,300. The number and relative amounts of these components varied considerably with ripeness and variety of tomato, and no single extract contained all four. The four forms diflFered in heat stability and response to pH and cation concentration. The fourth form, the major species in most tomato extracts, had properties similar to those of the enzyme described by Lee and Macmillan (75), whose molecular weight, however, was estimated on Sephadex G-75 as 27,500 (81),... 

Two forms of pectinesterase, apparently similar in molecular weight but differing in charge and response to cation concentration, have been demonstrated in limes and oranges. In the orange, one form was located in the peel while the other was located within the segment covers and juice sacs. 

Three multiple forms of pectinesterase have been found in extracts and purified products from carrot. The enzymes (mol. wts. 2.7 x 10 ) were found to possess properties similar to those of tomato pectinesterase. 

Pectinesterases.—The pectinesterase activities in tomatoes stored at different temperatures have been determined. The level of activity is low in mature green fruit but increased rapidly at ca. 20 °C - but not at either 4 or 33 C. The storage-life of tomatoes kept at 33 °C for several days is increased, owing to suppression of the polygalacturonase activity. Multiple forms of the enzyme are responsible for the pectinesterase activity of tomatoes one of the forms has been characterized. ... 

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