Pectinesterase

About: Pectinesterase is a research topic. Over the lifetime, 724 publications have been published within this topic receiving 22461 citations. The topic is also known as: pectase & pectin methoxylase.

Pectin methylesterase, a regulator of pollen tube growth

Abstract: The apical wall of growing pollen tubes must be strong enough to withstand the internal turgor pressure, but plastic enough to allow the incorporation of new membrane and cell wall material to support polarized tip growth. These essential rheological properties appear to be controlled by pectins, which constitute the principal component of the apical cell wall. Pectins are secreted as methylesters and subsequently deesterified by the enzyme pectin methylesterase (PME) in a process that exposes acidic residues. These carboxyls can be cross-linked by calcium, which structurally rigidifies the cell wall. Here, we examine the role of PME in cell elongation and the regulation of its secretion and enzymatic activity. Application of an exogenous PME induces thickening of the apical cell wall and inhibits pollen tube growth. Screening a Nicotiana tabacum pollen cDNA library yielded a pollen-specific PME, NtPPME1, containing a pre-region and a pro-region. Expression studies with green fluorescent protein fusion proteins show that the pro-region participates in the correct targeting of the mature PME. Results from in vitro growth analysis and immunolocalization studies using antipectin antibodies (JIM5 and JIM7) provide support for the idea that the pro-region acts as an intracellular inhibitor of PME activity, thereby preventing premature deesterification of pectins. In addition to providing experimental data that help resolve the significance and function of the pro-region, our results give insight into the mechanism by which PME and its pro-region regulate the cell wall dynamics of growing pollen tubes.

The Chemistry and technology of pectin

Abstract: [Contents without contributors--WR 10/29/91] CONTENTS: Function of Pectin in Plant Tissue Structure and Firmness Jams, Jellies, and Preserves Other Pectin Food Products Tropical Fruit Products The Chemistry of High-Methoxyl Pectins The Chemistry of Low-Methoxyl Pectin Gelation Gelation of Sugar Beet Pectin by Oxidative Coupling Pectinesterase The Polygalacturonases and Lyases Analytical and Graphical Methods for Pectin Rheology of Pectin Dispersions and Gels Nonfood Uses of PectinChapter References Index

Overexpression of Pectin Methylesterase Inhibitors in Arabidopsis Restricts Fungal Infection by Botrytis cinerea

Abstract: Pectin, one of the main components of plant cell wall, is secreted in a highly methylesterified form and is demethylesterified in muro by pectin methylesterase (PME). The action of PME is important in plant development and defense and makes pectin susceptible to hydrolysis by enzymes such as endopolygalacturonases. Regulation of PME activity by specific protein inhibitors (PMEIs) can, therefore, play a role in plant development as well as in defense by influencing the susceptibility of the wall to microbial endopolygalacturonases. To test this hypothesis, we have constitutively expressed the genes AtPMEI-1 and AtPMEI-2 in Arabidopsis (Arabidopsis thaliana) and targeted the proteins into the apoplast. The overexpression of the inhibitors resulted in a decrease of PME activity in transgenic plants, and two PME isoforms were identified that interacted with both inhibitors. While the content of uronic acids in transformed plants was not significantly different from that of wild type, the degree of pectin methylesterification was increased by about 16%. Moreover, differences in the fine structure of pectins of transformed plants were observed by enzymatic fingerprinting. Transformed plants showed a slight but significant increase in root length and were more resistant to the necrotrophic fungus Botrytis cinerea. The reduced symptoms caused by the fungus on transgenic plants were related to its impaired ability to grow on methylesterified pectins.

Thermostability and orange juice cloud destabilizing properties of multiple pectinesterases from orange

Abstract: Three forms of pectinesterase, accounting for 95% of the activity in Navel orange, showed considerable differences in heat stability and orange juice cloud destabilizing properties. Pectinesterase I and II (isoenzymes) and a so-called high molecular weight pectinesterase were rapidly inactivated at 70°C, 60°C, and 90°C, respectively. In chilled juices (5°C) the high molecular weight pectinesterise was the only enzyme which rapidly produced methanol and destabilized the cloud. Although this enzyme represents only 5% of the total pectinesterase activity in Navel orange, it is thought that it is largely responsible for gelation which may occur in concentrates produced by the cut-back process.