Glucose with dipeptides

Fractionation of mycobacteria resulted in the identification of two cellular immunostimulatory components, trehalose dimycolate (TDM) and muramyl dipeptides (MDP). Both are normally found in association with the mycobacterial cell wall. TDM is composed of a molecule of trehalose (a disaccharide consisting of two molecules of a-D-glucose linked via an a 1-1 glycosidic bond), linked to two molecules of mycolic acid (a long-chain aliphatic hydrocarbon-based acid) found almost exclusively in association with mycobacteria. TDM, while retaining its adjuvanticity, is relatively non-toxic. 

The hormone-hke peptide incretin stimulates the release of insuhn by a feedback process that involves cleaving the molecule to an inactive form. The protease enzyme dipeptidal peptidase (DPP) in turn cleaves incretin, in effect inactivating this enzyme. Inhibition of DPP consequently extends the action of incretin. This inhibition thus prevents the increased levels of blood glucose that mark diabetes. The protease inhibitor vidagliptin, which is modeled in part on the terminal sequence in DPP, has been found to sustain levels of insulin in Type II diabetics. The inhibition is apparently reversible in spite of the presence in the structure of the relatively reactive a-aminonitrile function. Construction of one intermediate in the convergent synthesis comprises the reaction of amino adamantamine (21-1) with a mixture of nitric and... 

Amino acids, dipeptides, and some tripeptides are transported from the lumen of the intestine through the membrane of the brush border of the mucosal cells and into the cytoplasm, where the peptides are hydrolyzed to amino acids. Transport of peptides and amino acids is active and analogous to glucose transport i.e., they are transported, together with Na+, across the gut-cell membrane by specific transport proteins called Na+ symports. Between the gut lumen and the cytoplasm of the cell there is a concentration gradient of Na+ that is maintained by Na+/K+ ATPase at the base of the cell adjacent to the blood capillaries this Na+/K ATPase pumps Na+ from the cell into the blood. 

This product is probably formed by condensation (involving the Strecker degradation of an amino acid) of pyruvaldehyde with 2,3-pentanedione (Wang et al., 1969). It is formed in the Maillard reaction of the dipeptide Ala-Asp (alanine-aspartic acid) with glucose. 

Short peptides also react with D-glucose and related sugars unevenly. In a series of LysPxx dipeptides, the rates of FruLysPxx formation in methanol at 64 °C were in the following order for Pxx Leu>Arg>Ile>Phe>Ser>Val>Tyr>Lys>Ala>Gly, and the... 

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