Glucosyl bonds, energy

The combination of the oligosaccharide glucotransferase with the hydrolase and the cellobiose phosphorylase, then accounts fully for the conservation of the glucosyl bond energy predicted by the growth experiments. 

Wynn et al. have described a potential energy calculation which utilizes the non bonded interaction and a term for the electrostatic interaction with the inclusion of directed chargers , localized in certain atomic orbitals [192, 193]. With this potential, they obtained for the P-D-glucosyl-ceramide a conformation which is similar to the X-ray crystal structure of P-D-Gal-ceramide [194], The calculation of the a-D-NeuvVAc-(2-3)-P-o-Gal disaccharide shows a conformation with cp-ci = 120° (determined from the stereoplot presented in the publication) which is inconsistent with the data obtained by Sabesan et al. [191], who were able to show that their calculated conformation with (p = 165° is in agreement with NOE data. 

Fig. 15.9 Synthesis of mutan from sucrose by S. mutans. (a) Reaction of sucrose with glycosyl transferase (see text), (b) Fates of the products, (i) The sucrose is hydrolyzed at its glycoside bond (red O atom also shown in c-i). The glucose moiety b-i is briefly enzyme bound as indicated in [c(ii)] and polymerized to mutan by the enzyme interacting at the Cl and C3 positions. The fructose is transferred intracellularly and metabolized to lactose which is secreted. The fructose metabolism provides energy, (c) Glucosyl transferase mode of action (see text)...

Possible conformations of the disaccharide-peptlde sub-units of the peptido-glycans of Staphylococcus aureus and Micrococcus luteus have been studied by an energy-minimization procedure. " Contrary to earlier reports the favoured conformation of the disaccharide 2-acetamido-2-deoxy-/8-D-glucosyl-(l->4)-.A -acetylmuramic acid is different from that of cellulose or chitin. Three types of conformation, two compact and one extended, are postulated with all three being stabilized by intramolecular hydrogen bonds. Two different models were proposed for the three-dimensional arrangement of peptidoglycan in the cell wall. 

The high energy bond in a substituted glucosyl phosphate might be important for sucrose synthesis. The equilibrium constant for reaction (i) was shown to be 2 to 8 at 37° and pH 7.4, indicating that this reaction favors sucrose formation. As for sucrose phosphorylase, L-sorbose, D-xylulose and D-rhamnulose acted as acceptors to give the corresponding disaccharides °. 

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