Polygalacturonase inhibition

The Effect of Glycosylation of Eiutopolygalacturonases and Polygalacturonase Inhibiting Proteins on the Production of Oligogalacturonides... 

Richter, A. et al. (2006) Transgenic peas (Pisum sativum) expressing polygalacturonase inhibiting protein from raspberry (Ruhus idaeus) and stilbene synthase from grape (Vitis vinifera). Plant Cell Rep. 25, 1166-1173... 

Smith CJS, Watson CF, Ray J, Bird CR, Morris PC, Schuch W, Grierson D (1988) Antisense RNA inhibition of polygalacturonase gene expression in transgenic tomatoes. Nature 334 724-726... 

Table 1 shows some biochemical properties of the pectolytic enzymes present in pool 1. The pectin lyase/pectate lyase activities (pool I) and polygalacturonase activity (pool II) were not significantly affected by NH4+, Na+ and K+ (0,25 - 2,5mM), while Al +, p-mercaptoethanol, Hg2+, EDTA, Ba + and Zn+2 (2,5mM) inhibited 30-100% these activities. On the other hand, Ca2+, Mg + and Mn + at 2,5mM concentration activated 20-100% pectin/pectate lyases but Ca " " and Cu " " (2,5mM) inhibited polygalacturonase activity about 42 - 70%. 

Stem juice of Dieffenbachia maculata contains an inhibitor of fungal polygalacturonase. The inhibitor is non dializable and heat stable. The double reciprocal plot indicates that the inhibitor causes a mixed type of inhibition. The paper also describes the distribution of the inhibitor in different varieties of Dieffenbachia, and some of its properties. 

Effect of PG inhibitor concentration on PG activity Various amounts of inhibitor were added in the assay mixture and the degree of inhibition of polygalacturonase activity was measured which showed a linear relationship between inhibitor concentration and percent inhibition... 

Effect of substrate concentration on PG inhibitor Polygalacturonase activity was measured, with or without inhibitor, at different concentrations of the substrate in the reaction mixture to understand the mode of inhibition of polygalacturonase by D. maculata stem inhibitor. The data presented in Fig. 1 indicate that the nature of inhibition is mixed-type. The inhibitor affects both Km as well as Vmax of polygalacturonase. 

The magnitude of inhibition of polygalacturonase was found to be dependent on preincubation of inhibitor with the enzyme. Similar observations have been reported for other enzyme inhibitors (Shivaraj and Pattabiraman, 1980 Sharma and Pattabiraman, 1980 Padmanabhan and Shrasti, 1990). However, preincubation of the inhibitor with substrate did not show any effect on inhibitor activity. In contrast, Shivaraj and Pattabiraman (1980) and Buonocore et al. (1977), have observed inactivation of amylase inhibitor activity on pretreatment with starch. 

Lycopene synthesis in the rin mutant was enhanced by high 02 in the presence of 10 ppm ethylene (Frenkel and Garrison, 1976). On the other hand, ethanol inhibits ripening and the synthesis of tomato lycopene (Saltveit and Mencarelli, 1988). In addition, Sheehy et al. (1988) found that a reduction in polygalacturonase did not affect biosynthesis of lycopene. Lampe and Watada (1971) and Mohr (1979) pointed out that the lycopene content in tomato fruits may be increased by improving the practices at times of selection of varieties, fertilization and harvest. 

Other enzyme studies (employing species of Pythium) have shown that Terrazole decreases the activity of exocellulase, increases that of endocellu-lase, and is substantially without effect on that of polygalacturonase and pectin methyl esterase.484 It partially inhibits the incorporation of uridine diphosphateacetylglucosamine into chitin in the presence of chitin synthetase, in vitro 485... 

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