Carrot cell walls

The third described enzyme form with pH optimum about 4.7 [11, 4], we found in Fraction C - the fraction from carrot roots pulp (Fig. 2). We supposed that this form of exopolygalacturonase is relatively strongly bound on carrot cell walls and so it can be released only by higher salt concentrations. The approximative molecular mass determination on Superose 12 (Fig. 3c) showed the molecular mass about 50 000 for this form and the second, with more acidic pH optimum, form present in the fraction. The further characterization of these enzymes showed the exopolygalacturonase with pH optimum 4.7 to be identical with enzyme described sooner by Pressey and Avants [4] and exopolygalacturonase with pH optimum 3.8 to be identical with the enzyme from Fraction A. In conclusion, the exopolygalacturonase form with pH optimum 3.8 can be considered to be the main enzyme form present in carrot roots. 

Kang YH, Parker CC, Smith AC and Waldron KW. 2008. Characterization and distribution of phenolics in carrot cell walls. J Agric Food Chem 56(18) 8558-8564... 

Cho, Y. P., and M. J. Chrispeels Serine-O-Galactosyl Linkages in Glycopeptides from Carrot Cell Walls. Phytochemistry 15, 165 (1976). 

Comparison of the MHR with non-modified pectic hairy regions of apple cell wall, isolated in a mild and defined way, revealed great resemblance indicating that the modifications of the MHR during enzymic liquefaction were only minor. Analogous MHR fractions could be isolated from potato fibre, pear, carrot, leek, and onion tissue. 

Our two network model of the primary wall receives support from a variety of indirect observations. For example it has been shown Aat when a cell wall is regenerated by a carrot protoplast a homogalacturonan/ rhamnogalacturonan shell is laid down first, through which the cellulose/ hemicellulose network is later intercalated (8). Further evidence that pectin may form an independent network is seen in the fact that walls from suspension-cultured cells of tofnato Lycopersicon esculentum VF 36),... 

Shea, E.M., Gibeaut, D.M., and Carpita, N.C. (1989) Structural analysis of the cell walls regenerated by carrot protoplasts. Planta, 179 293-308. 

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 present paper demonstrates applications of combinations of cloned monocomponent enzymes, including combinations with rhamnogalacturonases, for production of cloud stable apple juice, gelation of fruits, degradation of soy cell walls, production of dietetic soy and production of carrot puree are demonstrated. 

Effect of a new canning process on cell wall pectic substances, calcium retention and texture of canned carrots... 

Both probably act in concert, although in a non-woody plant (carrot) it has been concluded that the importance of cell wall alterations was secondary to that of chemical defence (24). Only the cell wall alterations involved in defence will be considered further here. 

Stevens, B. ]. H., and R. R. Selven-dran. Structural features of cell-wall polysaccharides of the carrot Daucus carota. Carbohydr Res 1984 128(2) 321-333. 

Liners, F., Van Cutsem, P. (1992). Distribution of pectic polysaccharides throughout walls of suspension-cultured carrot cells - An immunocytochemical study. Protoplasma, 170,10-21. 

Incubation of D-[U-I4C]apiose with sterile Lemma minor (duckweed) produced less than 0.01% incorporation into the cell-wall polysaccharides.75 Most of the d-[U-i4C]apiose appeared as 14C02 some remained in solution in the medium and in the duckweed plants, primarily as degradation products of D-[U-14C]apiose, but not as the branched-chain sugar.75 There is an efficient synthesis of the [U-14C]apiose moiety of cell-wall polysaccharides from D-[U-14C]glucose under similar conditions.81 Of the plant tissues tested, only L. minor contained an enzyme system able to metabolize free apiose. Carrot, lettuce, and spinach tissues are unable to metabolize the free, branched-chain sugar.75... 

---