Melibiose 6-0-

The gradients of H, Na, and other cations and anions established by ATPases and other energy sources can be used for secondary active transport of various substrates. The best-understood systems use Na or gradients to transport amino acids and sugars in certain cells. Many of these systems operate as symports, with the ion and the transported amino acid or sugar moving in the same direction (that is, into the cell). In antiport processes, the ion and the other transported species move in opposite directions. (For example, the anion transporter of erythrocytes is an antiport.) Proton symport proteins are used by E. coU and other bacteria to accumulate lactose, arabinose, ribose, and a variety of amino acids. E. coli also possesses Na -symport systems for melibiose as well as for glutamate and other amino acids. 

It was found98 that the amount of sucrose consumed could be accounted for entirely as levan and reducing sugars. Fructose formed part of the reducing sugars produced, and there was no appreciable interconversion of aldose and ketose. When raffinose was used as substrate, the products were levan, melibiose and D-fructose (but not sucrose and D-galactose). The following equation expresses fully the net result of the action of the autolyzate ... 

The rate of oxidation of ethylene glycol was found268-269 to attain a broad maximum between pH 2.5 and 6. In a very complete study of the effect of pH on the periodate oxidation of carbohydrates, Neumiiller and Vasseur260 showed that the oxidation of maltose, melibiose, methyl a-D-... 

Melibiosone was prepared by the action of benzaldehyde on melibiose phenylosazone17-191 and was identified by conversion into melibiose p-bro-mophenylosazone. On treatment with emulsin, it was hydrolyzed to D-glucosone and D-galactose.17,203... 

In bacteria and yeasts, Li+ has strain-dependent, inhibitory, and morphological effects upon growth. The driving force behind the transport of carbohydrates and amino acids in bacteria is the proton gradient, and in both E. coli [228] and Salmonella typhimurium cells [229], Li+ stimulates the movement of proline into cells via a Li+/proline symport and the transport of melibiose via a cotransport pathway [230]. In both cases, Li+ is replacing Na+ and results in the inhibition of growth. 

Similarly, per-O-trimethylsilylated mono- and P-linked disaccharides (lactose and cellobiose, not melibiose) could be converted into the corresponding a-glycosyl iodides, which upon SN2 displacement with CbT using TBACN mainly afforded P-cyano derivatives in good overall yields [191]. The cyanoglycosides were transformed into aminomethyl glycosides via reduction under mild conditions (Scheme 2.52). 

The melibiose carrier MelB of E. coli is a well-studied sodium symport system. This carrier is of special interest, because it can also use protons or lithium ions for cotransport. The projection structure of MelB has been solved at 8 A resolution [107]. The 12 TM helices are arranged in an asymmetrical pattern similar to the previously solved structure of NhaA, which, however, follows an antiport mechanism (Na+ ions out of the cell and H+ into the cell). 

Hacksell, I., Rigaud, J. L., Purhonen, P., Pourcher, T., Hebert, H. and Leblanc, G. (2002). Projection structure at 8A resolution of the melibiose permease, an Na-sugar co-transporter from Escherichia coli, EMBO J., 21, 3569-3574. 

That melibiose-l-phosphate cannot react with fructofuranose is inferred from the inability of the enzyme to phosphorolyze raffinose. 

The naturally-occurring 1,6-linked glucose polymers furnish other sources of 2,3,4-trimethyl-D-glucose, which has been isolated from the hydrolysis products of the methyl ethers of gentiobiose,112 118 melibiose,114 raffmose106 116 and dextran.78 74,116... 

C HgaOn-HaO 6-0-a-D-Galactopyranosyl-a,/3-D-glucopyranose monohydrate Q ,/3-melibiose monohydrate (MELIBM10)71... 

Disaccharides cellobiose and cellobiulose, (gentiobiose, isomaltose, kojibiose, laminarabiose, leucrose, melibiose, nigerose, palatinose, sophorose, trehalose, turanose, and xylobiose), lactose and lactulose, maltose and maltulose ... 

---