Of invertase

Balasundaram B, Pandit AB (2001) Selective release of invertase by hydrodynamic cavitation. Biochem Eng J 8 251-256... 

Bell et al. (2002) investigated the relationship between water mobility as measured by oxygen-17 NMR (transverse relaxation rate obtained from linewidth at half-height) and chemical stability in glassy and rubbery polyvinylpyrrolidone (PVP) systems. Reported results suggest that water mobility in PVP model systems was not related to Tg. The study did not find a link between water mobility and reaction kinetics data (half-lives) for degradation of aspartame, loss of thiamin and glycine, and stability of invertase. 

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. 

A final example is the work of Wolfram and Shafizadeh1 8 on the structure of sucrose, for which Hudson had given an a-D configuration for the o-glucopyranosyl moiety, based on the results of invertase-catalyzed hydrolysis. These workers,128 using data from the methyl n-fructofuranosides, demonstrated that this hydrolysis is not accompanied by a Walden inversion and that the original work of Hudson was correct. 

The biosynthesis in yeast of two enzymes that are D-mannoproteins has been studied. A membrane-associated isozyme of invertase (EC 3.2.1.26) has been shown to be a precursor of the external invertase.190 Its molecular weight, as determined by SDS-poly(acrylamide) gel electrophoresis, is 50,000, that is, smaller than that of the external invertase, and it correlates well with the presence of only the inner-core sugars of the final form. It is strictly bound to membranes, possibly those of the endoplasmic reticulum, and it can be completely split191 by endo-/3-N-acetylglucosaminidase H (EC 3.2.1.30). The addition of tunicamycin, which specifically inhibits formation of d-GIcNAc-PP-DoI, inhibits synthesis of external invertase, as well as further formation of the membrane-associated form, which completely disappears after addition of the antibiotic.190 In these aspects, the synthesis of this extracellular enzyme follows the pathway for secreted glycoproteins in animal systems. 

Production of Invertase-sensitive Material from Melezitose by Proteus... 

Invertase hydrolyzes cane sugar into glucose and fructose. The following table shows the amount of sugar inverted in the first 10 minutes of reaction for various initial substrate concentrations. The amount of invertase was set constant. 

Sasaki, T., Tadokoro, K. Suzuki, S. (1971). Multiple forms of invertase of potato tuber stored at low temperature. Phytochemistry 10, 2047-50. 

The feasibility of amperometric sucrose and mercury biosensors based on the immobilization of invertase, glucose oxidase, and muta-rotase entrapped in a clay matrix (laponite) was investigated by Mohammadi et al. [31]. In this work, the effect of pH of a tri-enzymatic biosensor in which the optimum pH of the three enzymes is different (Invertase, pH 4.5 Glucose oxidase, pH 5.5 and Mutarotase, pH 7.4) [41] was studied. The pH effect on the biosensor response was analyzed between pH 4 and 8 and the highest activity was found at pH 6.0. In order to improve the selectivity of the invertase toward mercury and to avoid silver interference, a medium exchange technique was carried out. The biosensor was exposed to mercury in an acetate buffer solution at pH 4 while the residual activity was evaluated with phosphate buffer solution at pH 6 [41]. 

Perform the experiments on mercury inhibition in two steps. In the first, a volume of 10 mL of buffer solution containing known concentration of invertase incubate with 10 mL of toluene solvent. 

Since the invertase enzyme was purchased 2 years ago from the time this experiment is performed, it was necessary to determine its activity. Knowing that an enzymatic unit corresponds to the amount of enzyme causing the transformation of 1.0 pM of substrate per minute. The equivalent of the response of the enzyme has been given in concentration of the substrate from the linear regression equation of the glucose response. For both sucrose and glucose the experiments have been done in the same conditions of pH value and applied potential. After extrapolation of the invertase response we have found that the activity of invertase is equal to 140 U/mg. 

The degree of inhibition in function of the concentration of the enzyme was studied in presence of 50 ppb of the inhibitor using the biphasic system (aqueous/toluene) as described in the experimental part. The concentration of invertase was varied from 0.05 to 4 gg/mL. 

The sensitivity of invertase toward methyl mercury using the clean-up method can be improved using the low amount of invertase (0.05 pg/mL) with 10 min of incubation time and kipping the hydrolysis reaction time for more than 10 min. 

Fig. 20.4. Calibration curve for inhibition of invertase (0.05 pg/mL) by methyl mercury after 10-min incubation using biphasic system (phosphate buffer/ toluene mixture) and glucose oxidase biosensor. Eapp — +0.60 V vs. Ag/AgCl and reaction time = 5 min.

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