Enzymes invertase

Sucrose on hydrolysis with dilute acids, or with the enzyme invertase (or ju-crase p. 514,) gives rise to one molecule of glucose and one molecule of fructose ... 

Enzymes. Invertase (P-fmctofuranosidase) is commercially produced from S. cerevisiae or S. uvarum. The enzyme, a glycoproteia, is not excreted but transported to the cell wall. It is, therefore, isolated by subjecting the cells to autolysis followed by filtration and precipitation with either ethanol or isopropanol. The commercial product is available dry or ia the form of a solutioa containing 50% glycerol as a stabilizer. The maia uses are ia sucrose hydrolysis ia high-test molasses and ia the productioa of cream-ceatered candies. 

At a partieular room temperature, results for the hydrolysis of suerose, S, eatalyzed hy the enzyme invertase (Cg = 1 x 10 mol in a hateh reaetor are given hy ... 

Competitive inhibition is important in biological control mechanisms for instance, if the product assumes the role of an inhibitor. The enzyme invertase catalyzes the hydrolysis of sucrose into glucose and fructose. As glucose is a competitive inhibitor, it ensures that the reaction does not proceed too far. 

Yeast Fermenting in Dough. When yeast is in a bread dough the traces of sugars present can be fermented directly. As yeast contains the enzyme invertase, any sucrose present can be inverted into dextrose and fructose which can then be fermented. If any dextrose from a high DE glucose syrup is present then it can be directly fermented. If there is any lactose present it can not be fermented at all. Similarly, any polyols such as sorbitol can not be fermented. 

The hydrolysis of sucrose (S) catalyzed by the enzyme invertase has been studied by measuring the initial rate, rPo, at a series of initial concentrations of sucrose (cSo). At a particular temperature and enzyme concentration, the following results were obtained (Chase et al., 1962) ... 

Several papers investigating the inversion of sucrose into glucose and fructose appeared a decade ago [133,174, 175]. The reaction is performed using the enzyme invertase according to the following reaction ... 

In most European countries, honey is defined in similar terms. However, certain quality factors considered by Europeans, especially the Germans, of importance in the marketing of honey are the levels of the enzymes invertase and diastase, and of 5-(hydroxymethyl)-2-furaldehyde. White has discussed these requirements in relation to suggested standards for the Codex Alimentarius.32 The German insistence on these requirements is outlined in a volume of Apiacta.33... 

The enzyme invertase catalyzes the hydrolysis of sucrose to glucose and fructose. The rate of this enzymatic reaction decreases at higher substrate concentrations. Using the same amount of invertase, the initial rates at different sucrose concentrations are given in Table P3.9. 

Sucrose ( cane sugar, beet sugar ), melting point I7Q-186°C (decomposes). With the enzyme invertase, yields glucose plus fructose. Specific rotatory power +66,4°,... 

Raffinose, melitose, melting point 118°C (anhydrous). With the enzyme invertase, yields fructose plus melibiose. With the enzyme emulsin, yields sucrose plus galactose. 

Q The rate of formation of the product P in the catalytic conversion of sucrose to fructose and glucose by the enzyme invertase is given by ... 

H. Mohammadi, A. Amine, A. Ouarzane and M. El Rhazi, Screening of fish tissue for methyl mercury using the enzyme invertase in a solvent interface, Microchim. Acta, 149 (2005) 251-257. 

Scheme 20.1. Glucose oxidase biosensor combined with the enzyme invertase in solution.

To assess the selectivity of our method, the fish samples have been spiked with 2 ppm of mercury (II) and then treated as described before. After toluene incubation with invertase enzyme (0.05 pg/mL) no effect has been observed on enzyme activity. The same amount of mercury (II) has been added in fish samples in presence of 0.4 ppm of methyl mercury. In this case, 50% of inhibition has been noted and corresponds exactly to the value obtained when we studied the calibration cure in absence of mercury (II) (Fig. 20.4). This result is in agreement with what is reported in the literature showing that the methyl mercury is much more soluble in organic solvents than the mercury ions [8]. In addition to this high selectivity of our method, we have shown previously that the enzyme invertase is selective for mercury [3]. In the presence of Zn2+, Cu2+, Cd2+, Pb2+ and Fe3+ no inhibition was detected for these cations. 

Daneben wird unter Inversion, weil sich dabei das Vorzeichen des Drehwertes andert, auch die Spaltung der rechtsdrehenden Saccharose in ein Gemisch von Glucose und Fructose (Invertzucker) durch ver-diinnte Sauren oder das Enzym Invertase verstanden. 

To explain their results on the conversion of sucrose to glucose and fructose by the enzyme invertase, Michaelis and Menten proposed in 1913 the following scheme of reactions ... 

A veiy important aspect of chemical kinetics is that dealing with the rates of enzyme-catalyzed reactions. Enzymes are a class of proteins that catalyze virtually all biochemical reactions. In this experiment we shall study the inversion of sucrose, as catalyzed by the enzyme invertase (/3-fractofuranidase) derived from yeast. The rate of the enzyme-catalyzed reaction will then be compared to that of the same reaction catalyzed by hydrogen ions. 

A special case arises when the "skin" (membrane) layer of a normal composite membrane element is immobilized with a catalyst and not intended for separating reaction species. Consider the example of an enzyme, invertase, for the reaction of sucrose inversion. Enzyme is immobilized within a two<layer alumina membrane element by filtering an invertase solution from the porous support side. After enzyme immobilization, the sucrose solution is pumped to the skin or the support side of the membrane element in a crossflow fashion. By the action of an applied pressure difference across the element, the sucrose solution is forced to flow through the composite porous structure. Nakajima et al. [1988] found that the permeate direction of the sucrose solution has pronounced effects on the reaction rate and the degree of conversion. Higher reaction rates and conversions occur when the sucrose solution is supplied from the skin side. The effect on the reaction rate is consistently shown in Figure 11.6 for two different membrane elements membrane A is immobilized by filtering the enzyme solution from the support layer side while membrane B from the skin layer side. 

---