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  • 1. Bollok, Monika
    et al.
    Henriksson, Hongbin
    Kallas, Åsa
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Jahic, Mehmedalija
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Teeri, Tula
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Enfors, Sven-Olof
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Production of plant xyloglucan endotransglycosylase (XET) using the methylotrophic yeast Pichia pastorisInngår i: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291Artikkel i tidsskrift (Annet vitenskapelig)
  • 2.
    Bollok, Monika
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Henriksson, Hongbin
    KTH, Skolan för bioteknologi (BIO).
    Kallas, Åsa
    KTH, Skolan för bioteknologi (BIO).
    Jahic, Mehmedalija
    KTH, Skolan för bioteknologi (BIO).
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO).
    Enfors, Sven-Olof
    KTH, Skolan för bioteknologi (BIO).
    Production of poplar xyloglucan endotransglycosylase using the methylotrophic yeast Pichia pastoris2005Inngår i: Applied Biochemistry and Biotechnology, ISSN 0273-2289, Vol. 126, s. 61-77Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The gene XET16A encoding the enzyme xyloglucan endotransglycosylase (XET) from hybrid aspen (Populus tremula x tremuloides Mich) was transformed into Pichia pastoris GS115 and the enzyme was secreted to the medium. The influence of process conditions on the XET production, activity, and proteolytic degradation were examined. Inactivation of XET occurred in the foam, but could be decreased significantly by using an efficient antifoam. Rich medium (yeast extract plus peptone) was needed for product accumulation, but not for growth. The proteolytic degradation of the enzyme in the medium was substantially decreased by also adding yeast extract and peptone to the glycerol medium before induction with methanol. Decreasing the fermentation pH from 5.0 to 4.0 further reduced the proteolysis. The specific activity was further improved by production at 15 degrees C instead of 22 degrees C. In this way a XET production of 54 mg/L active enzyme could be achieved in the process with a specific activity of 18 Unit/mg protein after a downstream process including centrifugation, micro- and ultrafiltration, and ion exchange chromatography.

  • 3. Johansson, P.
    et al.
    Brumer, Harry
    KTH, Tidigare Institutioner, Bioteknologi.
    Baumann, Martin J.
    KTH, Tidigare Institutioner, Bioteknologi.
    Kallas, Åsa
    KTH, Tidigare Institutioner, Bioteknologi.
    Henriksson, Hongbin
    KTH, Tidigare Institutioner, Bioteknologi.
    Denman, Stuart
    KTH, Tidigare Institutioner, Bioteknologi.
    Teeri, Tuula
    KTH, Tidigare Institutioner, Bioteknologi.
    Jones, A.
    Crystal structures of a poplar xyloglucan endotransglycosylase reveal details of the transglycosylation acceptor binding2004Inngår i: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 16, nr 4, s. 874-886Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Xyloglucan endotransglycosylases (XETs) cleave and religate xyloglucan polymers in plant cell walls via a transglycosylation mechanism. Thus, XET is a key enzyme in all plant processes that require cell wall remodeling. To provide a basis for detailed structure-function studies, the crystal structure of Populus tremula x tremuloides XET16A (PttXET16A), heterologously expressed in Pichia pastoris, has been determined at 1.8-Angstrom resolution. Even though the overall structure of PttXET16A is a curved beta-sandwich similar to other enzymes in the glycoside hydrolase family GH16, parts of its substrate binding cleft are more reminiscent of the distantly related family GH7. In addition, XET has a C-terminal extension that packs against the conserved core, providing an additional beta-strand and a short alpha-helix. The structure of XET in complex with a xyloglucan nonasaccharide, XLLG, reveals a very favorable acceptor binding site, which is a necessary but not sufficient prerequisite for transgilycosylation. Biochemical data imply that the enzyme requires sugar residues in both acceptor and donor sites to properly orient the glycosidic bond relative to the catalytic residues.

  • 4.
    Kallas, Åsa M.
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Piens, Kathleen
    KTH, Skolan för bioteknologi (BIO).
    Denman, Stuart E.
    KTH, Skolan för bioteknologi (BIO).
    Henriksson, Hongbin
    KTH, Skolan för bioteknologi (BIO).
    Fäldt, Jenny
    KTH, Skolan för kemivetenskap (CHE).
    Johansson, Patrik
    Brumer, Harry
    KTH, Skolan för bioteknologi (BIO).
    Teeri, Tuula T.
    KTH, Skolan för bioteknologi (BIO).
    Enzymatic properties of native and deglycosylated hybrid aspen (Populus tremula x tremuloides) xyloglucan endotransglycosylase 16A expressed in Pichia pastoris2005Inngår i: Biochemical Journal, ISSN 0264-6021, Vol. 390, s. 105-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The cDNA encoding a xyloglucan endotransglycosylase, PttXET16A, from hybrid aspen (Populus tremula x tremuloides) has been isolated from an expressed sequence tag library and expressed in the methylotrophic yeast Pichia pastoris. Sequence analysis indicated a high degree of similarity with other proteins in the XTH (xyloglucan transglycosylase/hydrolase) gene subfamily of GH16 (glycoside hydrolase family 16). In addition to the conserved GH16 catalytic sequence motif, PttXET16A contains a conserved N-glycosylation site situated proximal to the predicted catalytic residues. MS analysis indicated that the recombinant PttXET16A expressed in P. pastoris is heterogeneous due to the presence of variable N-glycosylation and incomplete cleavage of the a-factor secretion signal peptide. Removal of the N-glycan by endoglycosidase H treatment did not influence the catalytic activity significantly. Similarly, site-directed mutagenesis of Asn(93) to serine to remove the N-glycosylation site resulted in an enzyme which was comparable with the wild-type enzyme in specific activity and thermal stability but had clearly reduced solubility. Hydrolytic activity was detected neither in wild-type PttXET16A before or after enzymatic deglycosylation nor in PttXET16A N93S (Asn(93) -> Ser) mutant.

  • 5.
    Master, Emma
    et al.
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Rudsander, Ulla
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Zhou, Welin
    Henriksson, Hongbin
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Divne, Christina
    KTH, Tidigare Institutioner (före 2005), Bioteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Denman, Stuart
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Wilson, David
    Teeri, Tuula
    KTH, Tidigare Institutioner (före 2005), Bioteknologi.
    Recombinant Expression and Enzymatic characterization of PttCel9A, a KOR homologue from Populus tremula x tremuloides2004Inngår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 43, nr 31, s. 10080-10089Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PttCel9A is a membrane-bound, family 9 glycosyl hydrolase from Populus tremula x tremuloides that is upregulated during secondary cell wall synthesis. The catalytic domain of PttCel9A, Delta(1-105)PttCel9A, was purified, and its activity was compared to TfCel9A and TfCel9B from Thermobifida fusca. Since aromatic amino acids involved in substrate binding at subsites -4, -3, and -2 are missing in PttCel9A, the activity of TfCel9A mutant enzymes W256S, W209A, and W313G was also investigated. Delta(1-105)PttCel9A hydrolyzed a comparatively narrow range of polymeric substrates, and the preferred substrate was (carboxymethyl)cellulose 4M. Moreover, Delta(1-105)PttCel9A did not hydrolyze oligosaccharides shorter than cellopentaose, whereas TfCel9A and TfCel9B hydrolyzed cellotetraose and cellotriose, respectively. These data suggest that the preferred substrates of PttCel9A are long, low-substituted, soluble cellulosic polymers. At 30degreesC and pH 6.0, the k(cat) for cellohexaose of Delta(1-105)PttCel9A, TfCel9A, and TfCel9B were 0.023 +/- 0.001, 16.9 +/- 2.0, and 1.3 +/- 0.2, respectively. The catalytic efficiency (k(cat)/K-m) of TfCel9B was 39% of that of TfCel9A, whereas the catalytic efficiency of Delta(1-105)PttCel9A was 0.04% of that of TfCel9A. Removing tryptophan residues at subsites -4, -3, and -2 decreased the efficiency of cellohexaose hydrolysis by TfCel9A. Mutation of W313 to G had the most drastic effect, producing a mutant enzyme with 1% of the catalytic efficiency of TfCel9A. The apparent narrow substrate range and catalytic efficiency of PttCel9A are correlated with a lack of aromatic amino acids in the substrate binding cleft and may be necessary to prevent excessive hydrolysis of cell wall polysaccharides during cell wall formation.

  • 6.
    Svensson, Ingrid
    et al.
    KTH, Skolan för bioteknologi (BIO).
    Calles, Karin
    KTH, Skolan för bioteknologi (BIO), Bioprocessteknik.
    Lindskog, Eva
    KTH, Skolan för bioteknologi (BIO).
    Henriksson, Hongbin
    KTH, Skolan för bioteknologi (BIO).
    Eriksson, Ulrika
    KTH, Skolan för bioteknologi (BIO).
    Häggström, Lena
    KTH, Skolan för bioteknologi (BIO), Bioprocessteknik.
    Antimicrobial activity of conditioned medium fractions from Spodoptera frugiperda Sf9 and Trichoplusia ni Hi5 insect cells2005Inngår i: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 69, nr 1, s. 92-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Concentrated conditioned medium (CM) fractions from Spodoptera frugiperda Sf9 and Trichoplusia ni cells, eluting from a gel filtration column at around 10 kDa, were found to exhibit strong antibacterial activity against Bacillus megaterium and Escherichia coli. The B. megaterium cells incubated in the CM fraction from Sf9 cells rapidly lost viability: after 8 min the viability had decreased to 0.7%, as compared with the control. Addition of the CM fraction to E. coli cells resulted in a less drastic drop in viability: 65% viability was lost after 60 min of incubation. Further, exposure to the CM fraction caused a substantial leakage of intracellular proteins, as demonstrated by SDS-PAGE analysis. Cell lysis was confirmed by optical density measurements, microscopic investigations and flow cytometry. B. megaterium exposed to a CM fraction from T. ni cells lost 97% of their viability in about 40 min. Ubiquitin, thioredoxin and cyclophilin were identified in the antibacterial fraction from Sf9 cells by mass spectrometry and N-terminal amino acid sequencing. Other proteins in the fraction gave no matches in a database search. Since ubiquitin was shown not to cause the antimicrobial effect and thioredoxin and cyclophilin were likely not involved, the responsible agent may be an unknown protein, not yet registered in databases. The antimicrobial effect of the CM fraction from T. ni cells most probably comes from a lysozyme precursor protein.

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