Structural and thermodynamic properties of kappa class glutathione transferase from Camelus dromedarius.

The Arabian camel, Camelus dromedarius is naturally adapted to extreme desert climate and has evolved protective mechanisms to limit oxidative stress. The mitochondrial kappa class glutathione transferase enzyme is a member of GST supergene family that represents an important enzyme group in cellular Phase II detoxification machinery and is involved in the protection against oxidative stress and xenobiotics. In the present study, C. dromedarius kappa class glutathione transferase (CdGSTK1-1) was cloned, expressed in E. coli BL21, purified and its structural, thermodynamic and unfolding pathway was investigated. The results showed that CdGSTK1-1 has unique trimeric structure, exhibits low thermostability and a complex equilibrium unfolding profile. It unfolds through three folding states with formation of thinly populated intermediate species. The melting points (Tm) of the first unfolding transition was 40.3±0.2°C and Tm of the second unfolding transition was 49.1±0.1°C. The van't Hoff enthalpy of the first and second transition were 298.7±13.2 and 616.5±2.4kJ/mol, respectively. Moreover, intrinsic fluorescence and near-UV CD studies indicates that substrate binding does not leads to major conformational changes in CdGSTK1-1.

Genomics, phylogeny and in silico analysis of mitochondrial glutathione S-transferase-kappa from the camel Camelus dromedarius.

The domesticated one-humped camel, Camelus dromedarius, is one of the most important animals in the Arabian Peninsula. For most of its life, this species is exposed to both intrinsic and extrinsic genotoxic factors that cause gross DNA alterations in many organisms. GST enzymes constitute an important supergene family involved in protection against the deleterious effects of oxidative stress and xenobiotics. Cloning the camel mitochondrial GST kappa (GSTK) gene and comparing its structural similarities with different species may aid in understanding its evolutionary relics. We cloned the camel GSTK using RT-PCR. This yielded an open reading frame of 678 nucleotides, encoding a protein of 226 amino acid residues. In a comparative analysis, the cloned GSTK was used to screen orthologues from different organisms. Phylogenetic analysis demonstrated that the camel GSTK apparently evolved from an ancestral GSTK gene that predated the appearance of vertebrates, and it grouped with pig, cattle, dog, horse, human and monkey GSTKs. The calculated molecular weight of the translated ORF was 25.52 kDa and the isoelectric point was 8.4. The deduced cGSTK sequence exhibited high identity with many mammals, such as Bactrian camel (99.55%), pig, cattle and human (>74%), and lower identity with other unrelated organisms, such as frog (Xenopus tropicalis, 61%), chicken (Gallus gallus, 57%), salmon (Salmo salar, 49%), sponge (Amphimedon queenslandica, 46%), tick (Amblyomma maculatum, 45%) and roundworm (Caenorhabditis elegans, 33%). A 3D structure was built based on the crystal structure of the human and rat enzymes. The levels of cGSTK expression in five camel tissues were examined via real-time PCR. The highest level of cGSTK transcripts was found in the camel liver, followed by the testis, spleen, kidney and lung.

Enhanced production of lipase by the thermophilic Geobacillus stearothermophilus strain-5 using statistical experimental designs.

Statistically based experimental designs were applied to optimize the cultural conditions for the production of a glycerol-inducible lipase from the thermophilic Geobacillus stearothermophilus strain-5. The effect of nineteen culture conditions on enzyme production was evaluated using Plackett-Burman factorial design. Tween 80, K(2)HPO(4), glycerol and glucose were the most significant factors in improving enzyme production. The selected parameters were then further investigated using central composite design to define the optimal process conditions. Maximal enzyme activity (578 U/ml) was reached under the following conditions: glycerol, 2.24% (v/v); Tween 80, 0.76% (v/v); glucose, 0.76% (w/v) and K(2)HPO(4), 0.38% (w/v) which is about five folds the activity in basal medium. A verification experiment was carried out to examine model validation and revealed more than 98% validity.

Biodegradation of native feather keratin by Bacillus subtilis recombinant strains.

A mixed culture containing two recombinant Bacillus subtilis strains; was used to hydrolyze 1% chicken feather; both were previously transformed with late-expressed and early expressed alkaline protease (aprE) carrying plasmids pS1 and p5.2, respectively. Proteolytic and keratinolytic activities of the mixed culture increased in parallel with those of the culture of B. subtilis DB100 (p5.2), and both were higher than that of B. subtilis (pS1) cultures. On the other hand, data indicated that degradation of feather by the recombinant strains B. subtilis DB100 (p5.2), was greatly enhanced when using a previously optimized medium. High levels of free amino groups as well as soluble proteins were also obtained. The concentration of amino acids was considerably increased during the fermentation process. It was found that, the amino acids Phe, Gly and Tyr were the major amino acids liberated in the cultures initiated by both strains. Results render these recombinant strains suitable for application in feather biodegradation large scale processes.

Purification and characterization of two extracellular lipases from Pseudomonas aeruginosa Ps-x.

Two different extracellular lipases were isolated and purified from Pseudomonas aeruginosa Ps-x to apparent homogeneity using ammonium sulfate precipitation followed by ion exchange chromatography on Q- and S-Sepharose column. Both of the purified lipases are monomeric protein with molecular weight of 15.5 and 54.97 KDa respectively. The optimal activities of the enzymes were at 45 and 50 degrees C and pHs 10.0 and 9.0. Calcium ions increase thermostability of both purified lipases I and II. The purified lipase I showed no metal ion dependence for its activity since EDTA up to 10 mM has no effect on the enzyme activity. However purified lipase II showed slight inhibition by EDTA at the same concentration. Moreover, a serine protease inhibitor, PMSF showed an inhibitory effect on both purified enzymes.

Purification and characterization of extracellular Pseudomonas aeruginosa urate oxidase enzyme.

Urate oxidase (uricase) was isolated and purified from Pseudomonas aeruginosa to apparent homogeneity using ammonium sulphate precipitation followed by ion exchange and gel filtration chromatography. The specific activity of the purified uricase enzyme was found to be 636.36 with the use of uric acid as a substrate. The purified uricase enzyme is a monomeric protein with molecular weight of 64 kilodaltons. The optimal pH and temperature of the purified enzyme is 9.0 and 30 degrees C, respectively. The effect of some metal ions was studied. Sulphate forms of Fe+2, Zn+2 and Co+2 inhibit the uricolytic activity whereas; NaCl and CaCl2 enhance the enzyme activity. Moreover, the purified enzyme is inhibited by EDTA and KCN.

Identification, cloning and expression of Pseudomonas aeruginosa Ps-x putative urate oxidase gene in Escherichia coli.

In a previous study we reported for the first time the isolation and characterization ofurate oxidase enzyme from Pseudomonas aeruginosa. In this work we isolated and cloned a 1.350 kilobase DNA fragment that encode a putative urate oxidase gene from the genomic library of P. aeruginosa Ps-x. The nucleotide sequence of the cloned DNA insert revealed an open reading frame that encodes a protein of a molecular weight of 54.0 kDa. The cloned DNA fragment showed an uricolytic activity when expressed in E. coli DH5alpha. Surprisingly, the nucleotide sequence of the cloned gene showed more than 99% identity to the gene encoding hypothetical protein of P. aeruginosa PAO1. Moreover, the sequence of the cloned gene was closely similar to the corresponding uricase gene of Cellulomonas flavigena (44% similarity), but showed lower similarity values to that of Bacillus sp. BT-90 (24% similarity), Candida utilis (24% similarity). Interestingly, the isolated uricase gene showed closer similarity to uricase from yeast-like symbiotic fungi Beauveria bassiana (35%), Tolypocladium inflatum (29%), Paecilomyces tenuipes (27%) and Cerataphis fransseni (24%).

Evidence for the presence of active cytochrome P450 systems in Schistosoma mansoni and Schistosoma haematobium adult worms.

Extracts of the adult worms of both Schistosoma mansoni and Schistosoma haematobium can metabolise some typical P450 substrates but to differing degrees. S. mansoni worm extracts displayed a approximately 12-fold higher specific activity for an aminopyrine substrate than rat liver microsomes. At 4 mM substrate concentration the demethylation reaction with N-nitrosodimethylamine (NDMA) (5 nmol HCHO/mg protein/min) was only half that of rat liver microsomes, whereas in extracts of S. haematobium, no detectable activity was found towards NDMA. Using ethylmorphine as substrate the demethylation activity of S. mansoni extracts (1.82 nmol HCHO/mg protein/min) was 5.5-fold lower than that of rat liver microsomes. Benzphetamine demethylase activity was also readily detectable in S. mansoni worm extracts at 6.79 nmol HCHO/mg protein/min compared with 10.20 nmol HCHO/mg protein/min in the case of rat liver microsomes. When aniline was used as substrate, surprisingly, no activity was found in worm extracts of either S. mansoni or S. haematobium, whereas rat liver microsomes showed high activity towards this amine. The anti-P450 2E1 and 2B1/2 cross-reacted with both worm homogenates and gave a specific band corresponding to a protein of molecular weight of approximately 50.0 kDa. A study with anti-P450 IVA antibody revealed that while this protein was strongly expressed in S. haematobium worm extracts, no immunoreactivity was observed with extracts of S. mansoni. Immunoblotting analyses with anti-P450 IIIA and P450 1A1 did not detect immunoreactive protein in either S. mansoni or S. haematobium.