scholarly journals The hydrolysis of glycosyl fluorides by glycosidases. Determination of the anomeric configuration of the products of glycosidase action

1971 ◽  
Vol 123 (4) ◽  
pp. 607-611 ◽  
Author(s):  
J. E. G. Barnett
Keyword(s):  
Glucose Oxidase ◽  
Galactose Oxidase ◽  
Coffee Bean ◽  
Enzymic Hydrolysis ◽  
Initial Product ◽  
Rapid Assay ◽  
Anomeric Configuration ◽  
Ph Stat ◽  
Hydrolysis Of

The enzymic hydrolysis of glycosyl fluorides is conveniently followed by using a pH-stat. Reactions involving glucosyl or galactosyl fluorides can also be followed by using glucose oxidase or galactose oxidase respectively. The pH-stat allows the rapid assay of intestinal α-glucosidase in crude homogenates. Use of glycosyl fluorides as substrates for glycosidases facilitates the polarimetric or g.l.c. determination of the anomeric nature of the initial product of hydrolysis. Hydrolysis by fungal amyloglucosidase proceeds with inversion of configuration whereas that by yeast and rat intestinal α-glucosidase, coffee-bean α-galactosidase and almond emulsin β-glucosidase proceeds with retention of configuration. β-d-Glucopyranosyl azide was not a detectable substrate for almond emulsin β-d-glucosidase.

scholarly journals Kinetics and Mechanism of Hydrolysis of Acetylthiocholine by Butyrylcholine Esterase

2002 ◽  
Vol 57 (11-12) ◽  
pp. 1072-1077 ◽  
Author(s):  
Karel Komers ◽  
Alexandr Čegan ◽  
Marek Link
Keyword(s):  
Acetic Acid ◽  
Kinetics And Mechanism ◽  
Kinetics Parameters ◽  
Mechanism Of Hydrolysis ◽  
Ph Stat ◽  
Stat Method ◽  
Ellman’S Method ◽  
Hydrolysis Of

Kinetics and mechanism of hydrolysis of acetylthiocholine by the enzyme butyrylcholine esterase was studied. The spectrophotometric Ellman’s method and potentiometric pH-stat method were used for continuous determination of the actual concentration of the products thiocholine and acetic acid in the reaction mixture. The validity of the Michaelis-Menten (Briggs-Haldane) equation in the whole course of the reaction under used conditions was proved. The corresponding kinetics parameters (Vm and KM) were calculated from the obtained dependences of concentration of thiocholine or acetic acid vs. time and compared. From this comparison the deciding kinetic role of the step producing thiocholine was derived. The values of initial molar concentration of the enzyme and of the rate constants of the kinetic model were estimated.

METHOD JUSTIFICATION OF Β-GALACTOSIDASE ACTIVITY OF ENZYME PREPARATION

1970 ◽  
pp. 65-68
Author(s):  
Е. М. Serba ◽  
М. B. Overchenko ◽  
N. I. Ignatova ◽  
М. Е. Medrish ◽  
L. V. Rimareva
Keyword(s):  
Glucose Oxidase ◽  
Performance Studies ◽  
Enzyme Hydrolysis ◽  
Hydrolysis Time ◽  
Enzyme Preparations ◽  
Optimum Parameters ◽  
Low Concentrations ◽  
Reliable Performance ◽  
Hydrolysis Of

Enzyme preparations - sources of β-galactosidase, are widely used in the dairy industry. However, there is no standardized methods to determine their activity. Existing methods differ by the type of substrate used, conditions of analysis and how to define the products of the hydrolysis. The aim of this work is to study the process of conversion biocatalytic milk sugar and experimental substantiation of methods of analysis of hydrolysis products, providing reliable results determine activity of β-galactosidase. Found that of chemical methods glucose oxidase showed a greater sensitivity towards low concentrations of the product of hydrolysis is glucose formed in the conversion process lactose. The results of testing showed that the mass concentration of the glucose formed in hydrolysis of lactose, HPLC tested, consistent with data obtained using the glucose oxidase method. Set optimum range, which was observed directly proportional to the level of glucose concentration rise in reaction mixture from the lengthy process and the concentration of enzyme:  hydrolysis time - from 10 to 20 min, produced   glucose - from 20 µcg to 40 mcg, while the mass of enzyme - 25.0·10-6, and from 40 mcg to 80 mcg, when mass -5,0·10-5 g.  When the values of absorbance of the reaction mixture ranged 0,045-0,300 to ensure reliable performance. Studies on determination of the activity of the enzyme preparations confirmed received experimental data and allowed to choose optimum parameters and conditions analysis for introducing them to the method for determining the activity β-galactosidase using glucose oxidase reagent: time of inactivation enzyme (control) -10 min.  in a boiling water bath, substrate - 2% solution of lactose, pH of the substrate-6,0, hydrolysis time 15 min. at 30° c.

Specific Determination of Sucrose in Honey

1977 ◽  
Vol 60 (3) ◽  
pp. 669-672
Author(s):  
Jonathan W White
Keyword(s):  
Standard Deviation ◽  
Glucose Oxidase ◽  
Selective Adsorption ◽  
Large Excess ◽  
Adsorption Method ◽  
Specific Determination ◽  
Preliminary Separation ◽  
Hydrolysis Of ◽  
Repetitive Analysis

Abstract This paper describes a procedure for determining sucrose in honey without its preliminary separation. Interference from the large excess of glucose is removed by treating with glucose oxidase-catalase, and then the glucose from invertase hydrolysis of sucrose is measured. Sucrose is difficult to measure in honey because of its low concentration and the presence of at least 24 other sugars. Standard deviation between duplicates for 50 honey samples containing from 0.06 to 10.6% sucrose was 0.19; no known honey sugars interfered. The selective adsorption method for separating sucrose from interfering oligosaccharides is too slow for repetitive analysis of honey for sucrose only, although it is 8 times more sensitive than the procedure described. Results of analysis of 13 honey samples for sucrose by this procedure (averaging 1.66%) and the selective adsorption method (averaging 1.59%) did not differ significantly.

New Method for the Determination of the Half Inhibition Concentration (IC50) of Cholinesterase Inhibitors

2013 ◽  
Vol 68 (3-4) ◽  
pp. 133-138 ◽  
Author(s):  
Markéta Kovářováa ◽  
Karel Komersa ◽  
Šárka Štěpánková ◽  
Patrik Pařík ◽  
Alexander Čegan
Keyword(s):  
Time Course ◽  
Cholinesterase Inhibitors ◽  
Ph Value ◽  
Batch Reactor ◽  
Measuring Cell ◽  
Inhibition Concentration ◽  
Different Types ◽  
Ph Stat ◽  
Hydrolysis Of

A new and simple analytical method is described for the determination of the IC50 values of the inhibitors of the hydrolysis of acetylcholine (ACh) or acetylthiocholine (ATCh) by cholinesterases. The method is based on monitoring the time course of the pH value during the uninhibited and inhibited reaction. It requires only a pH meter with a suitable pH measuring cell and a small thermostated stirred batch reactor. The method has been validated for twelve different types of cholinesterase inhibitors. The determined IC50 values are comparable to those obtained by independent, more complicated, and expensive methods (Ellman´s and pH-stat).

scholarly journals The acid and enzymic hydrolysis of O-acetylated sialic acid residues from rabbit Tamm–Horsfall glycoprotein

1972 ◽  
Vol 129 (3) ◽  
pp. 683-693 ◽  
Author(s):  
A. Neuberger ◽  
Wendy A. Ratcliffe
Keyword(s):  
Sialic Acid ◽  
Vibrio Cholerae ◽  
Clostridium Perfringens ◽  
Slow Rate ◽  
Alkaline Treatment ◽  
Side Chain ◽  
Hydroxyl Groups ◽  
Enzymic Hydrolysis ◽  
Hydrolysis Of

Rabbit Tamm–Horsfall glycoprotein and bovine submaxillary glycoprotein were both found to contain sialic acid residues which are released at a slow rate by the standard conditions of acid hydrolysis. These residues are also resistant to neuraminidases from Vibrio cholerae and Clostridium perfringens. This behaviour was attributed to the presence of O-acetylated sialic acid, since the removal of O-acetyl groups by mild alkaline treatment normalized the subsequent release of sialic acid from rabbit Tamm–Horsfall glycoprotein by acid and by enzymic hydrolysis. Determination of the O-acetyl residues in rabbit Tamm–Horsfall glycoprotein indicated that on average two hydroxyl groups of sialic acid are O-acetylated, and these were located on the polyhydroxy side-chain of sialic acid or on C-4 and C-8. These findings confirm the assumption that certain O-acetylated forms of sialic acid are not substrates for bacterial neuraminidases. Several explanations have been suggested to explain the effect of O-acetylation of the side-chain on the rate of acidcatalysed hydrolysis of sialic acid residues.

Use of Enzymes in the Determination of Added Lactose in Meat Products Containing Corn Sirup Solids

1964 ◽  
Vol 47 (4) ◽  
pp. 695-700
Author(s):  
Lester Hankin ◽  
Alphoxse F Wickroski
Keyword(s):  
Glucose Oxidase ◽  
Reducing Sugars ◽  
Meat Products ◽  
Enzymatic Method ◽  
Complete Hydrolysis ◽  
Dry Milk ◽  
Enzyme Method ◽  
Aoac Method ◽  
Hydrolysis Of

Abstract An enzymatic method is proposed to overcome the difficulties encountered with the AOAC yeast method for the determination of lactose in prepared meat products which also contain corn sirup solids in addition to nonfat dry milk. The AOAC method does not allow for complete hydrolysis of the corn sirup solids, and, when reducing sugars are calculated as lactose, inflated values are obtained since some of the unhydrolyzed reducing material from the corn sirup solids is measured. In the enzyme method, a combination of crude maltase and glucose oxidase are used to remove all reducing sugars except lactose. Preliminary yeast treatment is included either routinely or to remove sucrose, if present. Comparative values obtained on prepared frankfort samples showed that the enzyme method was superior to the AOAC method.

Sign in / Sign up

Export Citation Format

Share Document