Sugars digestion

Amylase Converts starchy complex carbohydrates to sugars Digestion... 

Digestion (Section 29.1) The first stage of catabolism, in which food is broken down by hydrolysis of ester, glycoside (acetal), and peptide (amide) bonds to yield fatty acids, simple sugars, and amino acids. 

The a-glucosidase inhibitors, acarbose (Precose) and miglitol (Glyset), lower blood sugar by delaying die digestion of carbohydrates and absorption of carbohydrates in the intestine. 

Olestra is a nondigestible plastic, made by adding eight fatty acid molecules to the sugar molecule sucrose. The fatty acids block access to the sugar, so enzymes can t break it down. The result is a molecule that behaves like a fat, but cannot be digested by humans. 

Figure 5.31 LC-electrospray-MS-MS spectrum of the column eluate at around 22 min in the analysis of the peptide mixture from the tryptic digest of glycoprotein TIME-EA4 from silkworm diapause eggs. Reprinted from Bioorg. Med. Chem., 10, Kurahashi, T., Miyazaki, A., Murakami, Y., Suwan, S., Franz, T., Isobe, M., Tani, M. and Kai, H., Determination of a sugar chain and its linkage site on a glycoprotein TIME-EA4 from silkworm diapause eggs by means of LC-ESI-Q-TOF-MS and MS/MS , 1703-1710, Copyright (2002), with permission from Elsevier Science.

With few exceptions, small particles of vegetable foods are generally stripped of their more accessible nutrients during digestion in the GI tract. In this way starch, protein, fat and water-soluble small components (sugars, minerals) are usually well absorbed. This is not always the case, however, for larger food particles or for molecules that cannot diffuse out of the celF tissue. Neither is it the case for the lipid-soluble components. These need to be dissolved in lipid before they can be physically removed from the cell to the absorptive surface, since the cell wall is unlikely to be permeable to lipid emulsions or micelles, and the presence of lipases will strip away the solvating lipid. 

The hydrolysis of zeaxanthin esters by a carboxyl ester lipase indeed enhanced both the incorporation of zeaxanthin in the micellar phase and uptake of zeaxanthin by Caco-2 cells. As mentioned earher, carotenoids can also be linked to proteins by specific bindings in nature and these carotenoid-protein complexes may slow the digestion process and thus make their assimilation by the human body more difficult than the assimilation of free carotenoids. Anthocyanins are usually found in a glycosylated form that can be acetylated and the linked sugars are mostly glucose, galactose, rhamnose, and arabinose. 

Sugar composition (mol%) of MHR population A and fractions I-IV, obtained after Sephacryl S200 size-exclusion chromatography of the digest of MHR population A with RGase [39]. 

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