Glycosylation hexose

Carbamoyl-glucuronide Glycosylation hexose (Glc) primary secondary amines... 

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. 

General acid catalysis by glutamic acid-35 represents at present the mechanism for lysozyme best able to explain the kinetic and structural data. For it to occur, however, distortion of the hexose ring in subsite D to a half-chair must take place so that relief of strain in the transition state will make bond breaking sufficiently easy. A question that must be answered for this picture to be tenable is whether relief of strain can so greatly facilitate bond breaking when the carbonium ion is a glycosyl ion [see also the discussion in Fife (1972) and Atkinson and Bruice (1974)]. 

Inhibition of glycosylation in virus-infected cells usually has dramatic effects on virus multiplication. This discovery prompted promulgation of a new concept in the experimental therapy of virus-induced diseases. Local treatment of the affected regions with 2-deoxy-D-arabtno-hexose led50n s02 to significant improvements in human-genital herpes infections, or Herpes simplex virus infection of the eye. 

It is necessary to postulate the existence of a previously unknown, modification reaction of glycosyl nucleotides, that is, deoxygenation at C-4, in order to explain the formation of 4-deoxy-D-arafc//io-hexose, a monosaccharide constituent of Citrobacter lipopolysaccharide.202 4-Deoxy-L-threo-hex-4-enuronic acid, found in Klebsiella K22 polysaccharide,203 may be formed through dehydration of the D-galacturonic acid group or residue, either in the glycosyl nucleotide, or in the polysaccharide. 

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