Cellobiose configuration

Mutarotation of Hydrolysis Products by Ex-1. The mutarotation of hydrolysis products from cellopentaitol by Ex-1 was investigated. For comparison those by S-l and F-l were observed. As shown in Figure 20, the mutarotation of hydrolysis products by Ex-1 (exclusively G2) increases, indicating that products are released in the / -cellobiose configuration. Entirely similar results were observed for the hydrolysis products by S-l and F-l (a mixture of Gi, G2, and reduced G3 in different proportion for each reaction mixture). Therefore, these cellulase components belong to the same group, as far as the mutarotation pattern is concerned. 

Both maltose and cellobiose have a free anomeric hydroxyl group that is not involved in a glycoside bond The configuration at the free anomeric center is variable and may be either a or (3 Indeed two stereoisomeric forms of maltose have been iso lated one has its anomeric hydroxyl group m an equatorial orientation the other has an axial anomeric hydroxyl... 

Configurational dependence of lJc-, c-v> values has been observed with acetates of [l -13C]-labelled cellobiose, laminarabiose, maltose, and nigerose, the a- and /3-linked disaccharides respectively giving29 the values of 46.5 and 49.2 Hz. 

Cellobiohydrolase I (CBH I, 1,4-jS-D-glucan-cellobiohydrolase, E.C. 3.2.1.91) is the main protein (ca. 60%) of the cellulase complex produced by T. reesei strains. CBH I hydrolyses crystalline cellulose, acid swollen cellulose and 4-methylumbelliferyl-cellodex-trins by cleaving off the terminal cellobiose unit from the non reducing end of the chain. It operates with retention of configuration in the reaction products 19,20. The abundance of this enzyme and its stability has facihtated its purification to homogeneity... 

Figure 10. Relaxed (adiabatic) conformational energy map for p-maltose as computed by Brady and coworkers.i3 Contours are drawn at 2,4,6, 8, and 10 kcal/mol above the minimum near < ), y = -60°, -40°. The p-maltose structure may be derived from that of p-cellobiose in Fig. 1 by inversion of the stereochemical configuration at Cl.

The difference in frequency between the parallel type bonds in cellulose II and III and those of cellulose I is appreciable and suggests that the molecular form of the cellobiose residue is different in cellulose I from the other two modifications. However, since the frequency of a hydrogen-bonded OH group is very sensitive to the 0 0 distance, this difference in molecular configuration may not be very great. 

The constitution of both of these bioses has been established by Haworth et al. [15]. It was found that the compounds differed from one another in the spacial configuration of the oxygen bond (glucosidic bond) this linkage joins the carbon atoms 1 and 4 which occupy the /3-position in cellobiose, and the a-position in maltose ... 

In the disaccharide field intensity difference attributable to the configuration at the anomeric center had also been reported. Data presented by Kochetkov (55) indicated that such was the case with pertrimethyl-silylated a and /3, 1 - 4 and 1 - 6 glucosylglucoses. Vink et al. (56) concluded that the configuration at the anomeric center of the reducing unit was the most important factor influencing a set of ten peaks common to the spectra of pertrimethylsilylated a- and /3-lactose and / -cellobiose. Moreover, these workers used ratios of these ten peaks to distinguish a-lactose from its anomer. 

Four commonly occurring disaccharides. The configuration about the hemiacetal group has not been specified for lactose, maltose, or cellobiose because both anomers exist in equilibrium. 

The constitution and configuration of cellobiose was confirmed by synthesizing the sugar, though in very small yield. This was the first synthesis of cellobiose by way of a trityl compound. Methyl 2,3,6-tri-acetyl-/S-D-glucopyranoside (XXVII) was condensed with tetraacetyl-D-glucopyranosyl bromide and the condensation product identified as methyl heptaacetyl-(8-cellobioside (XXVIII). Since the latter compound yields acetobromocellobiose (heptaacetylcellobiosyl bromide) and cello-... 

---