Isolation and properties of xyloglucanases of <Emphasis Type="Italic">Penicillium</Emphasis> sp.

Using chromatographic technique, xyloglucanase (XG) A (25 kDa, pI 3.5, 12th glycosyl hydrolase family) was isolated from the enzyme complex secreted by the mycelial fungus Penicillium canescens, and xyloglucanases XG 25 (25 kDa, pI 4.1, 12th glycosyl hydrolase family) and XG 70 (70 kDa, pI 3.5, 74th glycosyl hydrolase family) were isolated from the enzyme complex of Penicillium verruculosum. Properties of the isolated enzymes (substrate specificity, optimal ranges of pH and temperature for enzyme activity and stability, effect of metal ions on catalytic activity) were compared with the properties of xyloglucanases XG 32 of Aspergillus japonicus, XG 78 of Chrysosporium lucknowense, and XG of Trichoderma reesei. The gene xegA encoding XG A of P. canescens was isolated, and the amino acid sequence of the corresponding protein was determined.     

Recombinant Endo-β-1,4-xylanase from Penicillium canescens

Recombinant endo-beta-1,4-xylanase (Xyl-31rec, 31 kD, pI 8.2-9.3, the tenth family of glycosyl hydrolases) was isolated from the culture liquid of Penicillium canescens (strain with the amplified homologous xylanase gene) by chromatofocusing on Mono P and hydrophobic chromatography on phenyl-Superose. It is shown that the biochemical and kinetic parameters, substrate specificity, stability, and other properties of the recombinant and native enzymes are almost the same. It was found that Xyl-31rec can be used for biobleaching of cellulose, the recombinant P. canescens strains providing a high yield of extracellular Xyl-31rec (up to 800-900 U/ml of culture liquid) and not secreting cellulases.     

Isolation and Properties of Major Components of Penicillium canescens Extracellular Enzyme Complex

The composition of the enzyme complex secreted by Penicillium canescens was investigated. A scheme for purification of the main components of the complex by chromatofocusing on a Mono P column was developed. It was found that along with beta-galactosidase, the major components of the complex were endo-beta-1,4-xylanase (31 kD, pI 8.2-9.3), alpha-L-arabinofuranosidase (60 kD, pI 7.6), arabinoxylan-arabinofuranohydrolase (70 kD, pI 3.8-4.0), and endo-beta-1,3/1,4-glucanase (40 kD, pI 4.4). The substrate specificity, pH and temperature activity optima, adsorbability, thermal stability, and ability for synergic interaction of the isolated enzymes were studied.     

Isolation and characterization of extracellular pectin lyase from Penicillium canescens

Pectin lyase A (molecular weight 38 kD by SDS-PAGE, pI 6.7) was purified to homogeneity from culture broth of the mycelial fungus Penicillium canescens using chromatographic techniques. During genomic library screening, the gene encoding pectin lyase A from P. canescens (pelA) was isolated and sequenced, and the amino acid sequence was generated by applying the multiple alignment procedure (360 residues). A theoretical model for the three dimensional structure of the protein molecule was also proposed. Different properties of pectin lyase A were investigated: substrate specificity, pH- and temperature optimum of activity, stability under different pH and temperature conditions, and the effect of Ca2+ on enzyme activity. In the course of the laboratory trials, it was demonstrated that pectin lyase A from P. canescens could be successfully applied to production and clarification of juice.     

Regulatory activity of heterologous gene-activator <Emphasis Type="Italic">xlnR</Emphasis> of <Emphasis Type="Italic">Aspergillus niger</Emphasis> in <Emphasis Type="Italic">Penicillium canescens</Emphasis>

The gene encoding the xlnR xylanolytic activator of the heterologous fungus Aspergillus niger was incorporated into the Penicillium canescens genome. Integration of the xlnR gene resulted in the increase in a number of activities, i.e. endoxylanase, β-xylosidase, α-L-arabinofuranosidase, α-galactosidase, and feruloyl esterase, compared to the host P. canescens PCA 10 strain, while β-galactosidase, β-glucosidase, endoglucanase, and CMCase activities remained constant. Two different expression constructs were developed. The first consisted of the nucleotide sequence containing the mature P. canescens phytase gene under control of the axhA promoter region gene encoding A. niger (1,4)-β-D-arabinoxylan-arabinofuranohydrolase. The second construct combined the P. canescens phytase gene and the bgaS promoter region encoding homologous β-galactosidase. Both expression cassettes were transformed into P. canescens host strain containing xlnR. Phytase synthesis was observed only for strains with the bgaS promoter on arabinose-containing culture media. In conclusion, the bgaS and axhA promoters were regulated by different inducers and activators in the P. canescens strain containing a structural tandem of the axhA promoter and the gene of the xlnR xylanolytic activator.     

Isolation and characterization of extracellular α-galactosidases from Penicillium canescens

Two alpha-galactosidases were purified to homogeneity from the enzymatic complex of the mycelial fungus Penicillium canescens using chromatography on different sorbents. Substrate specificity, pH- and temperature optima of activity, stability under different pH and temperature conditions, and the influence of effectors on the catalytic properties of both enzymes were investigated. Genes aglA and aglC encoding alpha-galactosidases from P. canescens were isolated, and amino acid sequences of the proteins were predicted. In vitro feed testing (with soybean meal and soybean byproducts enriched with galactooligosaccharides as substrates) demonstrated that both alpha-galactosidases from P. canescens could be successfully used as feed additives. alpha-Galactosidase A belonging to the 27th glycosyl hydrolase family hydrolyzed galactopolysaccharides (galactomannans) and alpha-galactosidase C belonging to the 36th glycosyl hydrolase family hydrolyzed galactooligosaccharides (stachyose, raffinose, etc.) of soybean with good efficiency, thus improving the digestibility of fodder.     

L-Arabinose induces synthesis of secreted beta-galactosidase in the filamentous fungus penicillium canescens

The mechanism of induction of secreted beta-galactosidase was studied in the filamentous fungus Penicillium canescens. L-Arabinose and its metabolite L-arabitol induce the synthesis of the enzyme. Apart from beta-galactosidase, L-arabinose induces the synthesis of other extracellular carbohydrolases including alpha-L-arabinofuranosidase. Increasing L-arabinose concentration above 1 mM or addition of other carbon sources results in carbon catabolite repression of the synthesis of the secreted enzymes. The data suggest that arabinofuranosidase can regulate the synthesis of secreted enzymes in P. canescens, thus controlling the level of free L-arabinose.     

Immunoexpression of aquaporins 1, 2, 3 and 4 in kidney of yak (Bos grunniens) on the Qinghai-Tibetan Plateau

Aquaporins (AQP) 1, 2, 3 and 4 belong to the aquaporin water channel family and play an important role in urine concentration by reabsorption of water from renal tubule fluid. Renal AQPs have not been reported in the yak (Bos grunniens), which resides in the Qinghai Tibetan Plateau. We investigated AQPs 1?4 expressions in the kidneys of Yak using immunohistochemical staining. AQP1 was expressed mainly in the basolateral and apical membranes of the proximal tubules and descending thin limb of the loop of Henle. AQP2 was detected in the apical plasma membranes of collecting ducts and distal convoluted tubules. AQP3 was located in the proximal tubule, distal tubule and collecting ducts. AQP4 was located in the collecting ducts, distal straight tubule, glomerular capillaries and peritubular capillaries. The expression pattern of AQPs 1?4 in kidney of yak was different from other species, which possibly is related to kidney function in a high altitude environment.