Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protein disulfide isomerase (PDI) was considered to be involved in the hepatic uptake of certain organic anions because the protein is photoaffinity labeled by photolabile derivatives of the bile acid taurocholate. Several lines of evidences including photoaffinity labeling experiments indicated a close relationship between the uptake of bile acids and the organic anion bumetanide. The possible involvement of PDI in hepatic transport processes of these organic anions was tested with polyclonal antibodies raised against a PDI-beta-galactosidase fusion protein. Western blot analysis and immunofluorescence of intact hepatocytes showed that protein disulfide isomerase is located in sinusoidal rat liver plasma membranes. This protein is immunologically identical with microsomal PDI prepared from bovine liver. The plasma membrane form of PDI is, however, not labeled by photoactivated bumetanide as revealed by two-dimensional gel electrophoresis. These results indicate that, although a membrane-bound form of the PDI is present in the sinusoidal plasma membrane of rat hepatocytes, this protein is not involved in the hepatocellular uptake of the organic anion bumetanide.
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PMID:A membrane-bound form of protein disulfide isomerase (PDI) and the hepatic uptake of organic anions. 827 87

The 3'-flanking region of the perfringolysin O (theta-toxin) gene (pfoA) of Clostridium perfringens was analyzed by chromosome walking. A total of 5,363 bp of the downstream region of the pfoA gene was sequenced and four open reading frames were found. ORF54 and ORF80 were found to be homologous to genes coding for membrane-bound transporter proteins of other bacteria and the beta-galactosidase gene (bgaB) of Bacillus stearothermophilus, respectively. ORF80 was named the pbg gene. Clones which showed beta-galactosidase activities were selected from a lambda FIXII genomic library of C. perfringens by blue plaque screening using X-Gal as a substrate. Four clones whose plaques showed blue appearances were obtained. Two of the four clones hybridized with the pbg probe but the others did not, indicating that there are two distinct beta-galactosidase genes in C. perfringens. The pbg gene was subcloned into pBR322 and was successfully expressed in Escherichia coli, suggesting that the pbg gene codes for a beta-galactosidase of C. perfringens.
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PMID:Sequence analysis of flanking regions of the pfoA gene of Clostridium perfringens: beta-galactosidase gene (pbg) is located in the 3'-flanking region. 857 81

The activity of all principal groups of lysosomal enzymes (acid phosphatase, lipase, beta-galactosidase, sulphatase and cathepsin B) was measured in the visual cortex of rabbits with experimental diabetes. In the first stage of diabetes (21 days), it was observed that enzyme activities in the free fraction and in the membrane-bound fraction are decreased as compared to the initial values determined in healthy animals. In the later stages of diabetes (90-180 days), all lysosomal enzyme activities increased except for sulphatase. This indicated a superiority of catabolic processes in visual cortex cells in the course of experimental diabetes.
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PMID:The activity of lysosomal enzymes in visual cortex of rabbits during experimental diabetes. 870 84

The secretion of the heterologous parathion phosphotriesterase in S. lividans using the Streptomyces beta-galactosidase signal sequence was further characterised using a pulse/chase system. Unsecreted cell-associated protein in both the precursor and signal-cleaved forms was observed when the protein was expressed from both low- and high-copy vectors. Fractionation of the cells followed by immunoprecipitation with phosphotriesterase antibody suggests that the precursor is membrane-bound while the signal cleaved form is present in the soluble fraction. Preliminary data on the processing of alpha-amylase, a native streptomyces protein, showed much more rapid processing and secretion, but nevertheless still revealed cell-associated, signal-cleaved protein.
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PMID:Native and heterologous protein secretion by Streptomyces lividans. 898 22

Lactase-phlorizin hydrolase (LPH) (EC 3.2.1.23/62), a major glycoprotein of the microvillus membrane of human small intestinal epithelial cells (enterocytes), is vital for the digestion of lactose during early infancy. The enzyme is synthesized in enterocytes as a single-chain precursor and subsequently proteolytically processed to the mature microvillus membrane-bound form. Because it has been reported that COS-1 cells were not able to proteolytically process LPH to the mature protein, these cells have been used as a model system to study potential roles of different proteases. COS-1 cells transfected with a full-length cDNA for human LPH synthesized enzymatically active enzyme. Immunoprecipitation of the expressed glycoproteins and their subsequent analysis by SDS-PAGE showed synthesis of two polypeptide species having apparent molecular masses of 210 and 220 kDa, respectively, corresponding to the high-mannose (pro-LPHh) form and the complex glycosylated (pro-LPHc) form of the LPH precursor. Surprisingly, an additional polypeptide species corresponding in size to the mature LPH found in human intestinal cells was also detected after longer chase periods. The source of this species was clearly pro-LPH, as its formation was inhibited by Brefeldin A. The cleaved form of LPH was not found on the cell surface; furthermore, its formation was prevented by an inhibitor of lysosomal function. We conclude from these data that in transfected COS-1 cells pro-LPH is transported to the cell surface, from which it is internalised and enters the lysosomal pathway, where proteolytic cleavage leads to a molecule not unlike mature LPH.
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PMID:Human lactase-phlorizin hydrolase expressed in COS-1 cells is proteolytically processed by the lysosomal pathway. 910 12

N-Acetyl-D-glucosaminylpyrophosphorylundecaprenol (GlcNAc-P-P-Und), an intermediate in the biosynthesis of the enterobacterial common antigen in E.coli and some O-antigen chains in gram-negative bacteria, is formed by the transfer of GlcNAc 1-P from UDP-GlcNAc to Und-P, analogous to the reaction forming GlcNAc-P-P-dolichol (GlcNAc-P-P-Dol) in mammalian cells. Since the microsomal enzyme from animal cells exhibits a strong preference for Dol-P, which contains a saturated alpha-isoprene unit, the polyisoprenyl phosphate specificity of the homologous bacterial enzyme was characterized. The enzyme remained bound to the membrane fraction when spheroplasts, formed by lysozyme-EDTA treatment, were lysed in hypotonic buffer. GlcNAc-P-P-Und synthase (GPT) activity was elevated in a strain of E.coli bearing the rfe gene, which encodes GPT on a multicopy plasmid, and virtually absent from rfe null mutants. GPT actively utilized fully unsaturated polyprenyl phosphate (Poly-P) substrates with maximal activity seen with (C55) Und-P, but was unable to utilize (C55)Dol-P. This substrate specificity contrasts with the microsomal GPT from pig brain, which actively utilized (C55)Dol-P, but not Und-P, as substrate. GPT activity bound to particulate fractions from three strains of bacilli also exhibited a strict preference for fully unsaturated Poly-P substrates. Unexpectedly, E.coli GPT activity cofractionated with the cytosolic marker enzyme, beta-galactosidase, and not the membrane-bound enzyme, D-lactate dehydrogenase, in cells disrupted in a French pressure cell. The properties and polyisoprenyl phosphate specificity of the soluble form of GPT were identical to the activity associated with the membrane preparations obtained from spheroplasts. The evolutionary and functional significance of the use of polyisoprenyl glycosyl carrier lipids with saturated alpha-isoprene units in eukaryotes remains uncertain.
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PMID:Polyisoprenyl phosphate specificity of UDP-GlcNAc:undecaprenyl phosphate N-acetylglucosaminyl 1-P transferase from E.coli. 913 38

Procyclic forms of Trypanosoma brucei have been genetically modified to express the major metacyclic variant surface glycoprotein (VSG variant AnTat 11.17) of Trypanosoma gambiense. The VSG is expressed in an intact membrane-bound form that can be detected over the entire plasma membrane, together with procyclin, and as a series of lower-molecular-mass fragments that are mostly soluble degradation products. The presence of degraded VSG in the cells and the culture medium suggests that VSG is not efficiently processed and/or efficiently folded when expressed in procyclic cells. The level of procyclin expressed on the surface of these cells is slightly reduced, although there is no difference in procyclin mRNA levels. The intact membrane-bound form of the VSG is N-glycosylated with oligomannose structures and contains a glycosylphosphatidylinositol (GPI) membrane anchor that can be biosynthetically labelled with [3H]ethanolamine. The anchor is sensitive to mammalian GPI-specific phospholipase D but, like the anchor of procyclin, it is resistant to the action of bacterial phosphatidylinositol-specific phospholipase C. This pattern of phospholipase sensitivity suggests that the GPI anchor acquired by VSG when expressed in procyclics is acylated on the inositol ring and therefore resembles a procyclic procyclin-type anchor rather than a trypomastigote VSG-type anchor with respect to the lipid structure. The VSG expressed in procyclics was sensitive to the action of a mixture of sialidase, beta-galactosidase and beta-hexosaminidase, suggesting that the VSG GPI anchor also contains a sialylated polylactosamine side-chain modification similar to that described for procyclin. These results indicate that the nature of the protein expressed has little influence on the post-translational modifications performed in the secretory pathway of procyclic trypanosomes.
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PMID:Expression of a variant surface glycoprotein of Trypanosoma gambiense in procyclic forms of Trypanosoma brucei shows that the cell type dictates the nature of the glycosylphosphatidylinositol membrane anchor attached to the glycoprotein. 921 Apr 13

The membrane-bound CzcCBA protein complex mediates heavy metal resistance in Alcaligenes eutrophus by an active cation efflux mechanism driven by cation-proton antiport. The CzcA protein alone is able to mediate weak resistance to zinc and cobalt and is thus the central antiporter subunit. The two histidine-rich motifs in the CzcB subunit are not essential for zinc resistance; however, deletion of both motifs led to a small but significant loss of resistance to this cation. Translation of the czcC gene encoding the third subunit of the CzcCBA complex starts earlier than predicted, and CzcC is probably a periplasmic protein, as judged by the appearance of two bands after expression of czcC in Escherichia coli under control of the phage T7 promoter. Fusions of CzcC and CzcB with alkaline phosphatase and beta-galactosidase are in agreement with a periplasmic location of most parts of both proteins. Both CzcC and CzcB are bound to a membrane, probably the outer membrane, by themselves and do not need either CzcA or each other as an anchoring protein. Based on these data, a new working model for the function of the Czc system is discussed.
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PMID:New functions for the three subunits of the CzcCBA cation-proton antiporter. 937 29

The drrAB operon of Streptomyces peucetius encodes for resistance to the antibiotics doxorubicin and daunorubicin. Subcloning of the drrAB genes in Escherichia coli has previously been shown to result in expression of DrrA and DrrB proteins and resistance to doxorubicin in a sensitive strain of E. coli. DrrA, a peripheral membrane protein, binds ATP in a UV-catalyzed reaction in a doxorubicin-dependent manner; DrrB, a hydrophobic protein, is localized to the inner membrane of E. coli (Kaur, P. (1997) J. Bacteriol. 179, 569-575). The present study provides evidence that DrrB, the membrane component of the complex, is stably maintained in the cell only if DrrA is present. Furthermore, it was found that the catalytic component DrrA is in an active conformation only when it is in a complex with DrrB. In a subclone containing the drrB gene by itself, no DrrB protein could be detected, although a translational fusion of the first 15 amino acids of DrrB to beta-galactosidase indicated that DrrB is translated in the absence of DrrA. Upon co-transformation with a plasmid containing the drrA gene in trans, DrrB could again be detected in these cells. UV cross-linking studies with [alpha-32P]ATP showed that only the membrane-bound form of DrrA in cells containing both DrrA and DrrB was in a conformation competent to bind ATP. Chemical cross-linking studies also provided direct evidence for interaction between the two proteins. Based on these analyses, a model for interaction between DrrA and DrrB proteins is presented.
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PMID:Biochemical coupling between the DrrA and DrrB proteins of the doxorubicin efflux pump of Streptomyces peucetius. 965

Chloragocytes were isolated from the earthworm species Lumbricus terrestris. After mechanical dissociation and sedimentation through Percoll, a highly purified fraction of viable chloragocytes was obtained. The isolated chloragocytes accumulated the vital dye neutral red and reduced the tetrazolium dye MTT, thereby indicating cellular integrity. Time of flight flow cytometric analyses revealed a main population of large and highly granulated cells in the 30-33 microm size range. Hydrolase measurements showed that beta-D-N-acetyl-glucosaminidase and acid phosphatase exhibited the highest activities (146.6 and 24.9 mU/mg of protein, respectively), possibly indicating a major role for these 2 hydrolases in the physiological function of chloragocytes. In contrast, other acid hydrolases such as beta-D-galactosidase and beta-D-glucuronidase had specific activities of respectively 26 and 182 times lower than the glucosaminidase. The specific activity of the membrane-bound alkaline phosphatase was comparable to that of its acid counterpart (18.9 vs. 24.9 mU/mg of protein, respectively) and this level of activity may show an important trans-membrane activity in chloragocytes. The cytoplasmic and mitochondrial enzyme isocitrate dehydrogenase had a level of activity comparable to that of the exclusively cytoplasmic enzyme lactate dehydrogenase (6.6 vs. 8.1 mIU/mg of protein, respectively). When L. terrestris chloragocyte homogenates were separated on Percoll, results showed that hydrolases and dehydrogenases were mainly associated with the lighter materials that remained above the Percoll layer. Nonetheless, the detection of significant proportions (15-25%) of the total recovered activity of acid phosphatase and beta-galactosidase in the enriched chloragosome fraction supports the notion that some chloragosomes may be 'lysosome-like' organelles.
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PMID:Isolation, purification and partial characterization of chloragocytes from the earthworm species Lumbricus terrestris. 974 18


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