Esterification, enzymatic hydrolysis reverse

Water is a product of esterification reaction and a reactant for the hydrolysis (reverse reaction). Therefore, the initial water content (W) affects the equilibrium. For this enzymatic reaction, the equilibrium conversion increases as the initial water concentration decreases (figure 3). The water content affects the reaction in two ways the reaction rate is decreased along the course of reaction and the final conversion is lower because water concentration shifts the equilibrium towards the reactants. This effect has also been reported by other authors [6]. 

Enzymatic esterification in an organic solvent which is a reverse process of the hydrolysis described above, were examined and 1,2 5,6-, 50a, 1,2 3,4-di-O-cyclohexylidene-myo-inositol 48a and... 

Syntheses of aliphatic polyesters by fermentation and chemical processes have been extensively studied in a viewpoint of biodegradable materials. Recently, another approach of their production has been performed by using an isolated lipase or esterase as catalyst via nonbiosynthetic pathways under mild reaction conditions. Lipase and esterase are enzymes which catalyze hydrolysis of esters in an aqueous environment in living systems. Some of them can act as a catalyst for the reverse reactions, esterifications and transesterifications, in organic media (1-5). These catalytic actions have been expanded to enzymatic synthesis of polyesters. Figure 5 represents three major reaction types of lipase-catalyzed polymerization leading to polyesters (6-14,73). 

Some thirty years ago Swell et al. showed that the rat intestinal mucosa possesses an enzymatic activity which catalyzes the formation of cholesterol esters[46,47]. The enzyme was called Cholesterol Esterase and its properties were similar to those of the pancreatic cholesterol esterase. Over the past three decades Vahouny and colleagues extensively studied the properties of this enzyme, its subcellular localization, the possible sources and finally they proceeded to the purification of the enzyme[5,26,28,48]. The authors hypothesize that the pancreas secretes subunits of cholesterol esterase. In the intestinal lumen the subunits, in presence of trihydroxy bile acids, aggregate to the active enz3me which catalyzes the hydrolysis of cholesterol esters from a micellar substrate and at the optimal pH of 6.6. The enz3one is then absorbed and localizes mostly in the supernatant of the mucosal cells here, at the optimal pH of 6.2, cholesterol esterase operates in reverse inducing the esterification of cholesterol and speeding up its... 

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