Production optimization, purification, expression, and characterization of a novel α-L-arabinofuranosidase from Paenibacillus polymyxa

Background: α-L-Arabinofuranosidase (EC 3.2.1.55) catalyzes the hydrolysis of terminal α-L-1,2-, -1,3-, and -1,5- arabinofuranosyl residues in arabinose-containing polymers, and hence, it plays an important role in hemicellulose degradation. Herein, the bacterium Paenibacillus polymyxa, which secretes arabinofuranosidase with high activity, was selected for enzyme production, purification, and characterization. Results: Medium components and cultural conditions were optimized by the response surface method using shake flask cultures. Arabinofuranosidase production reached 25.2 U/mL under optimized conditions, which were pH 7.5, 28°C, and a basic medium supplemented with 1.5 g/L mannitol and 3.5 g/L soymeal. Furthermore, the arabinofuranosidase secreted by P. polymyxa, named as PpAFase-1, was partially purified from the supernatant using a DEAE Sepharose Fast Flow column and a hydroxyapatite column. The approximate molecular mass of the purified PpAFase-1 was determined as 56.8 kDa by SDS-PAGE. Protein identification by mass spectrometry analysis showed that the deduced amino acid sequence had significant similarity to the glycosyl hydrolase family 51. The deduced gene of 1515 bp was cloned and expressed in Escherichia coli BL21 (DE3) cells. Purified recombinant PpAFase-1 was active toward p-nitrophenyl-α-L-arabinofuranoside (pNPAraf). The Km and kcat values toward pNPAraf were 0.81 mM and 53.2 s−1 , respectively. When wheat arabinoxylan and oat spelt xylan were used as substrates, PpAFase-1 showed poor efficiency. However, a synergistic effect was observed when PpAFase-1 was combined with xylanase from Thermomyces lanuginosus. Conclusion: A novel GH51 enzyme PpAFase-1 was cloned from the genome of P. polymyxa and expressed in E. coli. This enzyme may be suitable for hemicellulose degradation on an industrial scale.

Differential Protein Expressions in Virus-Infected and Uninfected Trichomonas vaginalis

Protozoan viruses may influence the function and pathogenicity of the protozoa. Trichomonas vaginalis is a parasitic protozoan that could contain a double stranded RNA (dsRNA) virus, T. vaginalis virus (TVV). However, there are few reports on the properties of the virus. To further determine variations in protein expression of T. vaginalis, we detected 2 strains of T. vaginalis; the virus-infected (V⁺) and uninfected (V⁻) isolates to examine differentially expressed proteins upon TVV infection. Using a stable isotope N-terminal labeling strategy (iTRAQ) on soluble fractions to analyze proteomes, we identified 293 proteins, of which 50 were altered in V⁺ compared with V⁻ isolates. The results showed that the expression of 29 proteins was increased, and 21 proteins decreased in V⁺ isolates. These differentially expressed proteins can be classified into 4 categories: ribosomal proteins, metabolic enzymes, heat shock proteins, and putative uncharacterized proteins. Quantitative PCR was used to detect 4 metabolic processes proteins: glycogen phosphorylase, malate dehydrogenase, triosephosphate isomerase, and glucose-6-phosphate isomerase, which were differentially expressed in V⁺ and V⁻ isolates. Our findings suggest that mRNA levels of these genes were consistent with protein expression levels. This study was the first which analyzed protein expression variations upon TVV infection. These observations will provide a basis for future studies concerning the possible roles of these proteins in host-parasite interactions.