Purification, kinetics and spectral characterisation of a new versatile peroxidase from a Bjerkandera Sp. isolate

From the extracellular fluid of a novel strain of Bjerkandera sp., it was isolated, purified and identified the main enzyme responsible for Remazol Brilliant Blue R dye decolourisation. Such an enzyme is able to oxidise manganese, as well as veratryl alcohol and 2,6-dimethoxyphenol in manganese-independent reactions; hence, it can be included in the new group of versatile peroxidases. The molecular mass of said enzyme is ca. 45 kDa, and the N-terminal amino acid sequence obtained by Edman degradation is VAXPDGVNTA. The enzyme substrate range for oxidation of several phenolic and non-phenolic aromatic compounds was determined and the corresponding Michaelis-Menten kinetic constants calculated. Furthermore, spectrophotometric assays showing the Soret band and allowing observation of band shifts of the enzyme led to the conclusion that Bjerkandera strains may also synthesise at least two different versatile peroxidases, as happens with Pleurotus eryngii

Evolution de la végétation dans une tourbière haute du plateau des Hautes-Fagnes après 20 ans (fagne Wallonne).

peer reviewe

Rapports sur le mémoire de R.M.M. Crawford intitulé :Morphological and metabolic changes in the apical bud with relation to photoperiodism in Salvia splendens

info:eu-repo/semantics/published5e séri

The spontaneous ability of normal human IgG to inhibit the Fc receptors of normal human monocytes is related to their binding capacity to lectins

The lectin-binding capacity of 96 normal human IgG, assessed by solid-phase radioimmunoassay, strikingly varied according to the lectin considered. Indeed, half of the IgG samples exhibited peanut agglutinin (PNA)- and pokeweed mitogen-specific binding capacities superior or equal to 4%, whereas less than 15% of IgG similarly bound to concanavalin A (Con A) and to phytohemagglutinin. The ability of those IgG to inhibit the Fc receptor (Fc-R) function of human monocytes, measured by a classical rosette assay, was inversely correlated to their binding ratios to PNA and Con A only. By affinity chromatography, three groups of IgG were separated: the IgG purified on agarose-PNA columns slightly reduced the Fc-R function (40-45% inhibition); the IgG purified on Sepharose-Con A columns exhibited the highest inhibitory properties (80-85% inhibition); the IgG that did not bind to PNA and Con A columns possessed intermediate inhibitory properties (65-70% inhibition). The different effect of IgG on Fc receptors was conserved when monocytes were first treated by trypsin and was unrelated to their specific binding to human monocytes, to their subclasses, and to their C1q- or protein A-binding capacities. Incubation of monocytes with D-galactose (10 mM) significantly improved their capacity to form IgG rosettes, whereas their incubation with D-mannose (10 mM) significantly reduced the Fc-R function. Scatchard plots of 125I-IgG1 myeloma protein binding to monocytes were linear under basal conditions, as well as after a prior incubation of the cells with D-galactose or D-mannose. Monocytes bound about 16,000 molecules of IgG1 per cell in each instance. In contrast, the mean association constant (Ka) for IgG1 binding was 2.59 +/- 0.50 X 10(8) M-1 under basal conditions, 4.4 +/- 0.75 X 10(8) M-1 after D-galactose incubation, and 1.35 +/- 0.50 X 10(8) M-1 after D-mannose incubation. These data suggest that the level of human monocyte Fc-R function blockade induced by human IgG depends mainly on the presence of "accessible" galactosyl or mannosyl residues in the Fc domain and that the modulation of the Fc-R function induced by these carbohydrates is due to a change in the affinity rather than in the number of single class of high-affinity binding sites