Enzymes glucosidation

Glucoside + inhibitor + enzyme glucoside-enzyme + inhibitor-enzyme... 

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. 

The glucosides are compounds, which, under the influence of hydrolytic agents are decomposed into glucose or an allied aldose or ketose, and one or more other bodies, which, in the cases under consideration, form constituents of essential oils. The hydrolytic agents which bring about these changes are soluble ferments, such as diastases, enzymes and similar... 

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-... 

Glucobrassicin is a mustard oil glucoside found in various Bras-sica spp. (50). 3-Indoleacetonitrile (IAN) is released from glucobrassicin by the action of the enzyme myrosinase at pH 4.0. How-... 

Enzymic and Chemical Synthesis of the a-l 2-glucosidic Linkage Enzymic Synthesis, S. A. Barker, E. J. Bourne, P. M. Grant, andM. Stacey, Nature, 178(1956) 1221-1223. 

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... 

If k2 > kj, the glycosyl-enzyme intermediate will accumulate, and may be trapped by the rapid denaturation of the enzyme in the presence of (saturating) amounts of substrate. With -glucoside Aj from Asp. wentii and 4-nitrophenyl [ C]-2-deoxy-) -D-irra />jo-hexopyranoside, it was possible to identify the intermediate as a glycosyl ester (acylal) of 2-deoxy-D-arabino-hexose bound to the same aspartate residue that had previously been labeled with the active-site-directed inhibitor conduritol B epoxide and with D-glucal." This constituted an important proof that the carboxylate reacting with the epoxide is directly involved in catalysis. 

In the second pathway, the (methylated or not) anthocyanin glucoside may be absorbed intact and serve as a snbstrate for the UDP-glncose dehydrogenase enzyme (GDH EC 1.1.1.22) that converts the glncose form into the corresponding glucu-ronide form, possibly in both hnman hver and small intestine. 

The yield of this (3-glucosidation would be controlled by the equilibrium of the coordination form of the enzyme. As illustrated in Fig. 3, the reaction site of the enzyme is proposed to be highly hydrophilic. To confirm the relationship... 

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