Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The subcellular distribution of sialyltransferase and its product of action, sialic acid, was investigated in the undifferentiated cells of the rat intestinal crypts and compared with the pattern observed in the differentiated cells present in the surface epithelium. Sialyltransferase was immunocytochemically detected with an antibody, affinity-purified on a beta-galactosidase/sialyltransferase fusion protein, which recognizes only protein epitopes of the enzyme. A similar pattern and intensity of immunolabeling were observed in the Golgi apparatus, apical and basolateral plasma membranes of both undifferentiated and differentiated absorptive cells. However, in the goblet cells, the mucus was only weakly labeled in cells present in the basal portion of the crypts but increased in intensity through the zone of migration to the surface epithelium. Sialic acid as detected with the Limax flavus lectin was observed in the Golgi apparatus and post-Golgi apparatus structures of both absorptive and goblet cells regardless of their position along the crypt-to-surface epithelium axis. However, a striking difference in the plasma membrane distribution of sialic acid existed between undifferentiated cells of the lower half of the crypts and those of the upper half and the surface epithelium: in the former, label was present in both the apical and basolateral domain, whereas in the latter it became restricted to the apical domain. These results suggest that the presence of sialyltransferase immunoreactivity in the goblet cell mucus and the polarization of sialic acid to the apical plasma membrane of both goblet and absorptive cells may be markers for the differentiated state.
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PMID:Alteration in sialyltransferase and sialic acid expression accompanies cell differentiation in rat intestine. 245 28

Starting from a tumor-associated synthetic MUC1-derived peptide MUC1a' and using a completely enzymatic approach for the synthesis of the core-2 sialyl Lewis X glycopart, the following glycopeptide was synthesized: AHGV[Neu5Ac(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-6)[Gal(beta1-3)]GalNAc(alpha1-O)]TSAPDTR. First, polypeptide N-acetylgalactosaminyltransferase 3 was used to site-specifically glycosylate MUC1a' to give MUC1a'-GalNAc. Then, in a one-pot reaction employing beta-galactosidase and core-2 beta6-N-acetylglucosaminyltransferase the core-2 O-glycan structure was prepared. The core-2 structure was then sequentially galactosylated, sialylated, and fucosylated by making use of beta4-galactosyltransferase 1, alpha3-sialyltransferase 3, and alpha3-fucosyltransferase 3, respectively, resulting in the sialyl Lewis X glycopeptide. The overall yield of the final compound was 23% (3.2 mg, 1.4 micromol). During the synthesis three intermediate glycopeptides containing O-linked GalNAc, Gal(beta1-4)GlcNAc(beta1-6)[Gal(beta1-3)]GalNAc, and Neu5Ac(alpha2-3)Gal(beta1-4)GlcNAc(beta1-6)[Gal(beta1-3)]GalNAc, respectively, were isolated in mg quantities. All products were characterized by mass spectrometry and NMR spectroscopy.
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PMID:Enzymatic synthesis of the core-2 sialyl Lewis X O-glycan on the tumor-associated MUC1a' peptide. 1277 Jul 66

In this paper we report that 3'-azido-3'-deoxythymidine (AZT) treatment of human erythroleukemia (K562) cells greatly alters the pattern of protein glycans and significantly modifies beta,(1 --> 4)galactosyltransferase, beta-galactosidase, and alpha,(2 --> 8)sialyltransferase activities. In particular, AZT-treated K562 cells exhibited a decreased incorporation of sialic acid (86% of control) into protein glycans, being the reduced alpha,(2 --> 6) incorporation almost of the same magnitude with respect to that of alpha,(2 --> 3) (93 and 90% of control, respectively). Moreover, the drug exposure of cells induced a decrease of both mannose terminally linked and galactose linked as beta,(1 --> 4) (90 and 92% of control, respectively) and a significant increase of galactose beta,(1 --> 3) (112% of control). In addition, beta,(1 --> 4)galactosyltransferase and beta-galactosidase activities were found enhanced in K562-treated cells (30 and 12%, respectively), while alpha,(2-8 )sialyltransferase activity decreased (75% of control). Sialyltransferase activities of other types i.e. 30, 60, 3 N, 6 N, did not show any appreciable differences irrespective of AZT-treatment. Besides previous studies which report that AZT exposure of K562 cells, indirectly prevents nucleotide-sugar import into the Golgi complex, with consequent inhibition of glycosylation, our observations show for the first time that AZT affects several enzymatic activities involved in specific glycosylation reactions leading, in turn, to protein glycans alteration.
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PMID:Protein glycans alteration and a different distribution of some enzymatic activities involved in the glycan processing are found in AZT-treated K562 cells. 1457 75