Hydrolysis enzymic, glucosides

The use of the enzyme system then known as invertin, which was extracted from beer yeast with water and precipitated from the aqueous solution, was available to Fischer when he began his classical studies of the enzymic hydrolysis of glucosides reported in 1894. The stage was also set by another enzyme known as emulsin, which Fischer purchased from E. Merck, Darmstadt, and which was known to hydrolyze several natural aromatic glucosides such as salicin, coniferin, arbutin, and the synthetic phenyl glucoside. These aryl glucosides were already known to not be cleaved by invertin. 

Additional studies of the enzyme-substrate complementarity in other complexes along the reaction path are under way. Since the initial report of an alternative pathway for lysozyme hydrolysis (8,9.28) work on the solution hydrolysis of glucosides has demonstrated the existence of a ring opening mechanism (29,30). ... 

This enzyme, which catalyzes the hydrolysis of glucosides, is a second example where Zn2+ may only play a structural role. The enzyme always contains Ca2+, which is necessary for catalytic activity, but the enzyme from Bacillus subtilis also contains zinc, which is thought to dimerize two monomeric units. However, there is some doubt over this matter, as the enzyme appears to exist as a monomer-dimer equilibrium in the absence of zinc. Zinc may then bind to the dimer only.532... 

An increase in residual sugar during the first six years of aging was noted by Ferr4 and Michel (1947). This they attributed to hydrolysis of glucosides—mainly of the oenin. The enzymes responsible were reported more prevalent in some years than in others. In two dry Swiss table wines Godet and Martin (1946) reported 0.026% and 0.024% glucose and 0.036% and 0.022% fructose, respectively. 

Microbial fermentation has appeared as a biotechnology alternative for biomaterial pretreat and for obtaining bioproducts metabolized by microorganism. Enzymes present in microbial fermentation are responsible for hydrolysis of glucosidic phenolics, increasing the release with increased solubility. 

Hydrolysis of glucosidic linkages by enzymes or/and acids - thin-boiling starches, acid - dex-trins,... 

Sinapine, CjgHjjOgN, was isolated as a thiocyanate from black mustard seeds (Brassica nigra) by Henry and Garot." Will and Laubenheimer first noted that sinapine occurs in white mustard seed in the form of the alkaloidal glucoside sinalbine, CajH jOuNgSg, which, on hydrolysis by the enzyme myrosin, also present in the seed, furnished dextrose, p-hydroxybenzylthiocarbimide and sinapine sulphate. Owing to its instability sinapine is unknown in the free state. The thiocyanate can be recrystallised from water and converted into the acid sulphate by treatment with sulphuric acid. 

It was of interest to determine whether glycosides of 6-deoxy-D-xylo-hex-5-enopyranose were susceptible to enzyme hydrolysis by / -glucosi-dase. Since aromatic glucosides are hydrolyzed by this enzyme at a much faster rate than aliphatic glycosides, phenyl 6-deoxy-/ -D-rt/Zo-hex-5-enopyranoside (18) was prepared (20). Phenyl / -D-glucopyranoside was converted to the 6-tosylate by selective esterification and then, by conventional procedures, transformed to phenyl 2,3,4-tri-0-acetyl-6-deoxy-... 

The type of intermediate that is formed in the slow inhibition with D-gly-cals was identified, with the aid of the ) -D-glucosidase A3 from Asp. wentii, as an ester of 2-deoxy-D-araA/ o-hexose with an aspartic acid side-chain. The same aspartoyl residue had already been shown, by labeling with con-duritol B epoxide (see Section 111,1), to be essential for -D-glucoside hydrolysis. In addition, this aspartate was found to form a glycosyl -enzyme... 

The effectiveness of proteolytic, amylolytic, and lipolytic detergent enzymes is based on enzymatic hydrolysis of peptide, glucosidic, or ester linkages. The mainstay of the market has been the protease types. 

Fischer was intrigued by the fact that emulsin caused hydrolysis of both / -glucosides and / -galactosides but had no effect on either the a- or / -xylo-sides (33). Since, at the time, Fischer expected glycosides to be furanosides, he suggested that both the enzymes required the presence of a free hydroxyl group at position 5 of a hexoside. 

CGTase Activity Assay. Aaivity was measured by the Pharmacia Phadebas Amylase Assay at pH 6.0, 60 C in O.IM sodium acetate (100 ppm Ca+ " ) for 15 minutes using B, stearothermophilus alpha-amylase as a standard. Alpha-amylase preparations were assayed under the same conditions. One Phadebas unit is defined as the amount of enzyme that will catalyze the hydrolysis of 1.0 micromole of glucosidic linkages of Lintner starch per minute at 6OOC, pH 6.0. 

The main cyanogenic glycoside in laurel is prunasin, the P-o-glucoside of benzaldehyde cyanohydrin. The enzymic hydrolysis of prunasin may be visualized as an acid-catalysed process, first of all hydrolysing the acetal linkage to produce glucose and the cyanohydrin. Further hydrolysis results in reversal of cyanohydrin formation, giving HCN and benzaldehyde. 

Hydrolysis of glycosides can also be achieved by the use of specific enzymes, e.g. P-glucosidase for P-glucosides and P-galactosidase for P-galactosides. 

Also referred to as endo-l,4-j8-glucanase and carboxy-methyl cellulase, this enzyme [EC 3.2.1.4] catalyzes the endohydrolysis of l,4-j8-D-glucosidic linkages in cellulose. The enzyme also catalyzes the hydrolysis of 1,4-Unkages in /3-D-glucans also containing 1,3-Unkages. 

This enzyme [EC 3.2.1.60] removes successive maltote-traose residues from the nonreducing chain ends by hydrolysis of l,4-a-D-glucosidic linkages in amylaceous polysaccharides. 

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