Enzymes glycosyl transfer

M. L. Sinnott, Catalytic mechanisms of enzymic glycosyl transfer, Chem. Rev. 90 1171 (1990). G. W. J. Fleet, Homochiral compounds from sugars, Chem. Br. 25 287 (1989). 

Sinnott, M.L. Catalitic Mechanisms of Enzymic Glycosyl Transfer. 1990 [95]... 

STEREOCHEMISTRY AND STEADY-STATE KINETICS OE ENZYMIC GLYCOSYL TRANSFER... 

Isotope effects for AMP nucleosidase demonstrate a very important feature of transition states for enzymic glycosyl transfer, namely that they are plastic, in the sense that their structure can be altered by comparatively minor changes in the protein. ATP is an allosteric activator and the fact that the relative magnitudes of the various effects alter according to allosteric activation mean that transition state structures must be changing (a change in commitments would have affected all effects equally). 

Sinott ML (1990) Catalytic mechanism of enzymic glycosyl transfer. Chem Rev 90 1171-1202... 

Transferases. Enzymes which transfer a group, possibly a methyl group or a glycosyl group, from one compound to another. The name of the group transferred is usually in-... 

For pectinolytic enzymes no glycosyl transfer reaction have been reported except for D-galacturonan digalacturonohydrolase (EC 3.2.1.82) from Selenotnonas ruminantium [4]... 

Hen egg white lysozyme is a small protein of Mr 14 500 and 129 amino acid residues. This enzyme was introduced in Chapter 1, where it was pointed out that examination of the crystal structure of the enzyme stimulated most of the solution studies. Hen egg white lysozyme has the distinction of being the first enzyme to have had its structure solved by x-ray crystallography.207 It is an atypical member of the hexosaminidase class of glycosyl transfer enzymes. It catalyzes the hydrolysis of substrates with retention of stereochemistry. T4 lysozyme was for many years thought to have the same fold and mechanism of lysozyme, despite there being no sequence homology. But it has now been found that the T4 enzyme has inversion of configuration and so operates by a different mechanism.208,209 A mechanism proposed for the enzymatic reaction was based on the structure of the... 

D being a glycosyl group. The reaction occurs in two main steps, formation of a glycosyl enzyme, and transfer of the glycosyl group to a water molecule. 

We thus elucidated that three of the four cellulase components are endo- or random-type and the other is exo-type. However, it is difficult to distinguish between the components of least or lowest random-type and those of exo-type. It is rather easy to identify an endo-type cellulase component. In contrast, it is very difficult to determine a cellulase to be exo-type because if the enzyme has a glycosyl-transferring activity the hydrolysis product is not a single sort, which is one of the necessary conditions to be an exo-type. Based on our experiments, measurement of the time course of CMC using a sample of medium substitution degree seems to be the best method of diagnosis to determine a cellulase component to be endo- or exo-type. With some enzymes, direction of mutarotation of reaction products is useful to resolve this problem, as is illustrated by the classic example of the starch hydrolysis by a- and /3-amylases. If this is true for our cellulases, the mutarotation of reaction products would be a... 

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