PubMed · 14304050
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P U CATALINO, M STIRPE, V VANNI. 1965-07-17. DISACCHARIDASE DEFICIENCY.. https://doi.org/10.1136/bmj.2.5454.128
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A series of mannosyl donors linked via position 2 to an m-xylylene or an isophthaloyl spacer which was connected to the position 6 of a glucoside acceptor afforded, via intramolecular glycosylation, the corresponding disaccharides with high beta anomeric ratio.
Oligosaccharyl transferase (OT) catalyzes the co-translational transfer of a dolichol-linked tetradecasaccharide (Dol-PP-GlcNAc(2)Man(9)Glc(3), 1a) to an asparagine side chain of a nascent polypeptide inside the lumen of the endoplasmic reticulum (ER). The glycosyl acceptor requires an Asn-Xaa-Thr/Ser sequon, where Xaa can be any natural amino acid except proline, for N-linked glycosylation to occur. To address the substrate specificity of the glycosyl donor, three unnatural dolichol-linked disaccharide analogues (Dol-PP-GlcNTFA-GlcNAc 1c, Dol-PP-2DFGlc-GlcNAc 1d, and Dol-PP-GlcNAc-Glc 1e) were synthesized and evaluated as substrates or inhibitors for OT from yeast. The synthetic analogue Dol-PP-GlcNAc-Glc 1e, with substitution in the distal sugar, was found to be a substrate (K(m)(app)() = 26 microM) for OT. On the other hand, the analogues Dol-PP-GlcNTFA-GlcNAc 1c (K(i) = 154 microM) and Dol-PP-2DFGlc-GlcNAc 1d (K(i) = 252 microM), with variations in the proximal sugar, were inhibitors for OT. The dolichol-linked monosaccharide Dol-PP-GlcNAc 3 was found to be the minimum unit for glycosylation to occur.
Standard methods were used for the study of the activity of brush border enzymes in the epithelium of the intestine of 45 human embryos aged from 4 to 22 weeks of the intrauterine life. Enzymes of the peptidase group (DPP IV, APM, APA, GGT, BBEP), of the phosphatase group (ALP, ACP, AMP, ATP), and of the disaccharidase group (saccharose, lactase, trehalase) were studied. In the embryonal developmental period (to week 8), the activity of proteases was mainly detected on the luminal surface of the primitive pseudostratified columnar epithelium of the intestine anlage. The highest activity was displayed by DPP IV. In the period from the 8th week, villi are formed from the duodenum up to the ileum. After week 9, differentiation of Lieberkühn crypts was observed. The activity of proteases was very high (DPP IV especially) in the differentiating microvillous zone of primitive enterocytes. Gradient of apex-base activity of the villus was maximal on the apex of villi. After week 12 of the intrauterine life, the activity of disaccharidases ALP and AMP occurs in the differentiating brush border, and a low activity of BBEP of the protease group is present.