A new xylanase from a Trichoderma harzianum strain.

A new xylanase (XYL2) was purified from solid-state cultures of Trichoderma harzianum strain C by ultrafiltration and gel filtration. SDS-PAGE of the xylanase showed an apparent homogeneity and molecular weight of 18 kDa. It had the highest activity at pH 5.0 and 45 degrees C and was stable at 50 degrees C and pH 5.0 up to 4 h xylanase. XYL2 had a low Km with insoluble oat spelt xylan as substrate. Compared to the amino acid composition of xylanases from Trichoderma spp, xylanase XYL2 presented a high content of glutamate/glutamine, phenylalanine and cysteine, and a low content of serine. Xylanase XYL2 improved the delignification and selectivity of unbleached hardwood kraft pulp.

Hydrolysis of xylans by enzyme systems from solid cultures of Trichoderma harzianum strains.

Xylanase activity was isolated from crude extracts of Trichoderma harzianum strains C and 4 grown at 28 degree C in a solid medium containing wheat bran as the carbon source. Enzyme activity was demonstrable in the permeate after ultrafiltration of the crude extracts using an Amicon system. The hydrolysis patterns of different xylans and paper pulps by xylanase activity ranged from xylose, xylobiose and xylotriose to higher xylooligosaccharides. A purified ss-xylosidase from the Trichoderma harzianum strain released xylose, xylobiose and xylotriose from seaweed, deacetylated, oat spelt and birchwood xylans. The purified enzyme was not active against acetylated xylan and catalyzed the hydrolysis of xylooligosaccharides, including xylotriose, xylotetraose and xylopentaose. However, the enzyme was not able to degrade xylohexaose. Xylanase pretreatment was effective for hardwood kraft pulp bleaching. Hardwood kraft pulp bleached in the XEOP sequence had its kappa number reduced from 13.2 to 8.9 and a viscosity of 20. 45 cp. The efficiency of delignification was 33%.

Hydrolysis of xylans by enzyme systems from solid cultures of Trichoderma harzianum strains

Xylanase activity was isolated from crude extracts of Trichoderma harzianum strains C and 4 grown at 28oC in a solid medium containing wheat bran as the carbon source. Enzyme activity was demonstrable in the permeate after ultrafiltration of the crude extracts using an Amicon system. The hydrolysis patterns of different xylans and paper pulps by xylanase activity ranged from xylose, xylobiose and xylotriose to higher xylooligosaccharides. A purified ß-xylosidase from the Trichoderma harzianum strain released xylose, xylobiose and xylotriose from seaweed, deacetylated, oat spelt and birchwood xylans. The purified enzyme was not active against acetylated xylan and catalyzed the hydrolysis of xylooligosaccharides, including xylotriose, xylotetraose and xylopentaose. However, the enzyme was not able to degrade xylohexaose. Xylanase pretreatment was effective for hardwood kraft pulp bleaching. Hardwood kraft pulp bleached in the XEOP sequence had its kappa number reduced from 13.2 to 8.9 and a viscosity of 20.45 cp. The efficiency of delignification was 33

Chemical synthesis of dendrotoxin-I: revision of the reported structure.

Dendrotoxin I (DTX-I) is a 60-residue peptide from the venom of the black mamba snake Dendroaspis polylepis, which binds to neuronal K+ channels. The structure reported previously for DTX-I was synthesized for the first time by a solution procedure. The synthetic product was confirmed to have the correct primary and disulfide structure determined by peptide mapping, sequence analysis and mass measurements. Comparison of synthetic DTX-I with the natural one by high-performance liquid chromatography and capillary zone electrophoresis, as well as by sequence analysis, revealed that the Asn residue at position 12 in the synthetic peptide was Asp in the natural product. Synthesis of DTX-I with Asp at position 12 gave a peptide identical with the natural product in all aspects. NMR analysis of synthetic [Asn12]- and [Asp12]-DTX-I also supported our findings that the Asn residue at position 12 in the DTX-I molecule should be revised as Asp. [Asn12]- and [Asp12]-DTX-I had very similar binding affinities when tested against radiolabeled dendrotoxin binding to rat brain synaptosomal membranes.

A new potassium channel toxin from the sea anemone Heteractis magnifica: isolation, cDNA cloning, and functional expression.

A new potassium channel toxin, HmK, has been isolated from the sea anemone Heteractis magnifica. It inhibits the binding of [125I]-alpha-dendrotoxin (a ligand for voltage-gated K channels) to rat brain synaptosomal membranes with a Ki of about 1 nM, blocks K+ currents through Kv 1.2 channels expressed in a mammalian cell line, and facilitates acetylcholine release at the avian neuromuscular junction. HmK comprises of 35 amino acids (Mr 4055) with the sequence R1TCKDLIPVS10ECTDIRCRTS20MKYRLNLCRK30TCGSC35. A full assignment of the disulfide linkages was made by using partial reduction with tri(2-carboxyethyl)phosphine (TCEP) at acid pH and rapid alkylation with iodoacetamide. The disulfide bridges were identified as Cys3-Cys35, Cys12-Cys28, and Cys17-Cys32. A cDNA clone encoding HmK was isolated using RT-PCR from the total RNA obtained from sea anemone tentacles, while the 5'- and 3'-flanking regions of the cDNA were amplified by RACE. The full-length cDNA was 563 bp long and contained a sequence encoding a signal peptide of 39 amino acids. The coding region for matured HmK toxin was cloned and expressed as a glutathione S-transferase (GST) fusion product in the cytoplasm of Escherichia coli. After affinity purification and cleavage, the recombinant toxin was shown to be identical to native HmK in its N-terminal sequence, chromatographic behavior, and binding to dendrotoxin binding sites on rat brain membranes.

On the convergent evolution of animal toxins. Conservation of a diad of functional residues in potassium channel-blocking toxins with unrelated structures.

BgK is a K+ channel-blocking toxin from the sea anemone Bunodosoma granulifera. It is a 37-residue protein that adopts a novel fold, as determined by NMR and modeling. An alanine-scanning-based analysis revealed the functional importance of five residues, which include a critical lysine and an aromatic residue separated by 6.6 +/- 1.0 A. The same diad is found in the three known homologous toxins from sea anemones. More strikingly, a similar functional diad is present in all K+ channel-blocking toxins from scorpions, although these toxins adopt a distinct scaffold. Moreover, the functional diads of potassium channel-blocking toxins from sea anemone and scorpions superimpose in the three-dimensional structures. Therefore, toxins that have unrelated structures but similar functions possess conserved key functional residues, organized in an identical topology, suggesting a convergent functional evolution for these small proteins.

Effect of the hydroalcoholic extract of rauwolfia ligustrina on smooth and cardiac muscles in-vitro.

The actions of the hydroalcoholic extract (HE) of Rauwolfia ligustrina (the whole plant) on agonist-induced contractions were analysed in the rat uterus and guinea-pig ileum and trachea, and also in rat atrium contracting spontaneously in-vitro. The HE (100-400 micrograms mL-1) caused concentration-dependent rightward shifts of the concentration-response curves and reduced the maximal contraction induced by oxytocin, bradykinin, angiotensin II, prostaglandin F2 alpha and acetylcholine in the rat uterus. The calculated mean IC50 values were: 300, 147, 158, 197 and 105 micrograms mL-1, respectively. In the guinea-pig ileum the HE also caused graded displacement to the right of the concentration-response curves for bradykinin, histamine and carbachol, associated with pronounced inhibition of the agonist-induced maximal contractions. The calculated mean IC50 values were 165, 134 and 241 micrograms mL-1, respectively. The HE (100-3000 micrograms mL-1) caused graded relaxation (IC50 of 271 micrograms mL-1) of strips of guinea-pig trachea precontracted with carbachol (0.2 microM). This effect was not influenced by propranolol (1 microM), 3-isobutyl-1-methylxanthine (1 microM) or methylene blue (10 microM), but was significantly potentiated (1.5-to 3-fold) by indomethacin (3 microM) and forskolin (1 nM). In addition, NG-monomethyl-L-arginine (L-NMMA, 100 nM) significantly reduced the HE-induced maximal relaxation, while indomethacin (3 microM) potentiated the HE response. Finally, the HE caused a concentration-dependent and long-lasting inotropic effect in the rat right atrium, contracting spontaneously with a mean EC50 value of 409 micrograms mL-1. It is suggested that the effects of the HE of R. ligustrina on smooth and cardiac muscles "in-vitro' may result from its ability to interact, at least partially, with the cAMP pathway.

[Prevalence of tardive dyskinesia among inpatients in psychiatric hospitals in Salvador, Bahia, Brazil]. / Prevalência de discinesia tardia em pacientes internados nos hospitais psiquiátricos de Salvador, Bahia, Brasil.

The authors present a cross-study on the occurrence of tardive dyskinesia (TD) among inpatients of psychiatric units of the city of Salvador during the month of September, 1992. After reviewing the literature, they comment the average prevalence found for TD: 1.65% in a population of 2,115 patients using a protocol based on the Simpson Scale.

Prevalência de discinesia tardia em pacientes internados nos hospitais psiquiátricos de Salvador, Bahia, Brasil / Prevalence of tardive dyskinesia on hospitalized patients in psychiatric hospitals from Salvador, Bahia, Brazil

Os autores apresentam estudo transversal da prevalência da discinesia tardia (DT) em pacientes internados em unidades psiquiátricas da cidade de Salvador durante o mês de setembro-1992. Após revisäo da literatura, comentam a prevalência média de DT encontrada: 1,65 por cento na populaçäo de 2115 pacientes, usando protocolo baseado na escala de Simpson