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  • Hegardt, Cecilia, et al. (författare)
  • Rapid caspase-dependent cell death in cultured human breast cancer cells induced by the polyamine analogue N-1,N-11-diethylnorspermine
  • 2002
  • Ingår i: European Journal of Biochemistry. - : Wiley-Blackwell. - 0014-2956. ; 269:3, s. 1033-1039
  • Tidskriftsartikel (refereegranskat)abstract
    • The spen-nine analogue N-1,N-11-diethylnorspermine (DENSPM) efficiently depletes the cellular pools of putrescine, spermidine and spermine by down-regulating the activity of the polyamine biosynthetic enzymes and up-regulating the activity of the catabolic enzyme spermidine/spermine N-1-acetyltransferase (SSAT). In the breast cancer cell line L56Br-Cl. treatment with 10 muM DENSPM induced SSAT activity 60 and 240-fold at 24 and 48 h after seeding. respectively, which resulted in polyamine depletion. Cell proliferation appeared to be totally inhibited and within 48 h of treatment, there was an extensive apoptotic response. Fifty percent of the cells were found in the sub-G(1) region, as determined by flow cytometry, and the presence of apoptotic nuclei was morphologically assessed by fluorescence microscopy. Caspase-3 and caspase-9 activities were significantly elevated 24 h after seeding, At 48 h after seeding, caspase-3 and caspase-9 activities were further elevated and at this time point a significant activation of caspase-8 was also found. The DENSPM-induced cell death was dependent on the activation of the caspases as it was inhibited by the general caspase inhibitor Z-Val-Ala-Asp fluoromethyl ketone. The results are discussed in the fight of the L56Br-Cl cells containing mutated BRCA1 and p53, two genes involved in DNA repair.
  • Karlsson, Johan, et al. (författare)
  • Homologous expression and characterization of Cel61A (EG IV) of Trichoderma reesei
  • 2001
  • Ingår i: European Journal of Biochemistry. - : Wiley-Blackwell. - 0014-2956. ; 268:24, s. 6498-6507
  • Tidskriftsartikel (refereegranskat)abstract
    • There are currently four proteins in family 61 of the glycoside hydrolases, from Trichoderma reesei, Agaricus bisporus, Cryptococcus neoformans and Neurospora crassa. The enzymatic activity of these proteins has not been studied thoroughly. We report here the homologous expression and purification of T. reesei Cel61A [previously named endoglucanase (EG) IV]. The enzyme was expressed in high amounts with a histidine tag on the C-terminus and purified by metal affinity chromatography. This is the first time that a histidine tag has been used as a purification aid in the T. reesei expression system. The enzyme activity was studied on a series of carbohydrate polymers. The only activity exhibited by Cel61A was an endoglucanase activity observed on substrates containing β-1,4 glycosidic bonds, e.g. carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC) and β-glucan. The endoglucanase activity on CMC and β-glucan was determined by viscosity analysis, by measuring the production of reducing ends and by following the degradation of the polymer on a size exclusion chromatography system. The formation of soluble sugars by Cel61A from microcrystalline cellulose (Avicel; Merck), phosphoric acid swollen cellulose (PASC), and CMC were analysed on a HPLC system. Cel61A produced small amounts of oligosaccharides from these substrates. Furthermore, Cel61A showed activity against cellotetraose and cellopentaose. The activity of Cel61A was several orders of magnitude lower compared to Cel7B (previously EG I) of T. reesei on all substrates. One significant difference between Cel61A and Cel7B was that cellotriose was a poor substrate for Cel61A but was readily hydrolysed by Cel7B. The enzyme activity for Cel61A was further studied on a large number of carbohydrate substrates but the enzyme showed no activity towards any of these substrates.
  • Lönn, Anna, et al. (författare)
  • Cold adaptation of xylose isomerase from Thermus thermophilus through random PCR mutagenesis. Gene cloning and protein characterization.
  • 2002
  • Ingår i: European Journal of Biochemistry. - : Wiley-Blackwell. - 0014-2956. ; 269:1, s. 157-163
  • Tidskriftsartikel (refereegranskat)abstract
    • Random PCR mutagenesis was applied to the Thermus thermophilus xylA gene encoding xylose isomerase. Three cold-adapted mutants were isolated with the following amino-acid substitutions: E372G, V379A (M-1021), E372G, F163L (M-1024) and E372G (M-1026). The wild-type and mutated xylA genes were cloned and expressed in Escherichia coli HB101 using the vector pGEM-T Easy, and their physicochemical and catalytic properties were determined. The optimum pH for xylose isomerization activity for the mutants was approximately 7.0, which is similar to the wild-type enzyme. Compared with the wild-type, the mutants were active over a broader pH range. The mutants exhibited up to nine times higher catalytic rate constants (k(cat)) for d-xylose compared with the wild-type enzyme at 60 degrees C, but they did not show any increase in catalytic efficiency (k(cat)/K(m)). For d-glucose, both the k(cat) and the k(cat)/K(m) values for the mutants were increased compared with the wild-type enzyme. Furthermore, the mutant enzymes exhibited up to 255 times higher inhibition constants (K(i)) for xylitol than the wild-type, indicating that they are less inhibited by xylitol. The thermal stability of the mutated enzymes was poorer than that of the wild-type enzyme. The results are discussed in terms of increased molecular flexibility of the mutant enzymes at low temperatures.
  • Månsson, Martin, et al. (författare)
  • Structural analysis of the lipopolysaccharide from nontypeable Haemophilus influenzae strain 1003
  • 2002
  • Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 269:3, s. 808-818
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural analysis of the lipopolysaccharide (LPS) of nontypeable Haemophilus influenzae strain 1003 has been achieved by the application of high-field NMR techniques, ESI-MS. capillary electrophoresis coupled to ESI-MS. composition and linkage analyses on O-deacylated LPS and core oligosaccharide material. It was found that the LPS contains the common structural element of H. influenzae, L-alpha-D-Hepp-(1 --> 2)-[PEtn --> 6]-L-alpha-D-Hepp-(1 --> 3)-[beta-D-Glcp-(1 --> 4)]-L-alpha-D-Hepp-(1 --> 5)-[PP Etn --> 4]-alpha-Kdop-(2 --> 6)-Lipid A. in which the beta-D-Glcp residue is substituted by phosphocholine at O-6 and an acetyl group at O-4. A second acetyl group is located at O-3 of the distal heptose residue (HepIII). HepIII is chain elongated at O-2 by either a beta-D-Glcp residue (major), lactose or sialyllactose (minor, i.e. alpha-Neu5Ac-(2 --> 3)-beta-D-Galp-(1 --> 4)-beta-D-Glcp), where a third minor acetylation site was identified at the glucose residue. Disialylated species were also detected. In addition. a minor substitution of ester-linked glycine at HepIII and Kdo was observed.
  • Achen, M G, et al. (författare)
  • Monoclonal antibodies to vascular endothelial growth factor-D block its interactions with both VEGF receptor-2 and VEGF receptor-3.
  • 2000
  • Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 267:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Vascular endothelial growth factor-D (VEGF-D), the most recently discovered mammalian member of the VEGF family, is an angiogenic protein that activates VEGF receptor-2 (VEGFR-2/Flk1/KDR) and VEGFR-3 (Flt4). These receptor tyrosine kinases, localized on vascular and lymphatic endothelial cells, signal for angiogenesis and lymphangiogenesis. VEGF-D consists of a central receptor-binding VEGF homology domain (VHD) and N-terminal and C-terminal propeptides that are cleaved from the VHD to generate a mature, bioactive form consisting of dimers of the VHD. Here we report characterization of mAbs raised to the VHD of human VEGF-D in order to generate VEGF-D antagonists. The mAbs bind the fully processed VHD with high affinity and also bind unprocessed VEGF-D. We demonstrate, using bioassays for the binding and cross-linking of VEGFR-2 and VEGFR-3 and biosensor analysis with immobilized receptors, that one of the mAbs, designated VD1, is able to compete potently with mature VEGF-D for binding to both VEGFR-2 and VEGFR-3 for binding to mature VEGF-D. This indicates that the binding epitopes on VEGF-D for these two receptors may be in close proximity. Furthermore, VD1 blocks the mitogenic response of human microvascular endothelial cells to VEGF-D. The anti-(VEGF-D) mAbs raised to the bioactive region of this growth factor will be powerful tools for analysis of the biological functions of VEGF-D.
  • Ademark, Pia, et al. (författare)
  • Cloning and characterisation of Aspergillus niger genes encoding an alpha-galactosidase and a beta-mannosidase involved in galactomannan degradation
  • 2001
  • Ingår i: European Journal of Biochemistry. - : Wiley-Blackwell. - 0014-2956. ; 268:10, s. 2982-2990
  • Tidskriftsartikel (refereegranskat)abstract
    • α-Galactosidase (EC and β-mannosidase (EC participate in the hydrolysis of complex plant saccharides such as galacto(gluco)mannans. Here we report on the cloning and characterization of genes encoding an α-galactosidase (AglC) and a β-mannosidase (MndA) from Aspergillus niger. The aglC and mndA genes code for 747 and 931 amino acids, respectively, including the eukaryotic signal sequences. The predicted isoelectric points of AglC and MndA are 4.56 and 5.17, and the calculated molecular masses are 79.674 and 102.335 kDa, respectively. Both AglC and MndA contain several putative N-glycosylation sites. AglC was assigned to family 36 of the glycosyl hydrolases and MndA was assigned to family 2. The expression patterns of aglC and mndA and two other genes encoding A. nigerα-galactosidases (aglA and aglB) during cultivation on galactomannan were studied by Northern analysis. A comparison of gene expression on monosaccharides in the A. niger wild-type and a CreA mutant strain showed that the carbon catabolite repressor protein CreA has a strong influence on aglA, but not on aglB, aglC or mndA. AglC and MndA were purified from constructed overexpression strains of A. niger, and the combined action of these enzymes degraded a galactomanno-oligosaccharide into galactose and mannose. The possible roles of AglC and MndA in galactomannan hydrolysis is discussed.
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