Lipoprotein lipase is active as a monomer

Lipoprotein lipase (LPL), the enzyme that hydrolyzes triglycerides in plasma lipoproteins, is assumed to be active only as a homodimer. In support of this idea, several groups have reported that the size of LPL, as measured by density gradient ultracentrifugation, is ∼110 kDa, twice the size of LPL monomers (∼55 kDa). Of note, however, in those studies the LPL had been incubated with heparin, a polyanionic substance that binds and stabilizes LPL. Here we revisited the assumption that LPL is active only as a homodimer. When freshly secreted human LPL (or purified preparations of LPL) was subjected to density gradient ultracentrifugation (in the absence of heparin), LPL mass and activity peaks exhibited the size expected of monomers (near the 66-kDa albumin standard). GPIHBP1-bound LPL also exhibited the size expected for a monomer. In the presence of heparin, LPL size increased, overlapping with a 97.2-kDa standard. We also used density gradient ultracentrifugation to characterize the LPL within the high-salt and low-salt peaks from a heparin-Sepharose column. The catalytically active LPL within the high-salt peak exhibited the size of monomers, whereas most of the inactive LPL in the low-salt peak was at the bottom of the tube (in aggregates). Consistent with those findings, the LPL in the low-salt peak, but not that in the high-salt peak, was easily detectable with single mAb sandwich ELISAs, in which LPL is captured and detected with the same antibody. We conclude that catalytically active LPL can exist in a monomeric state.

Prothrombin-Sepharose-Purified Factor V and Its Role in Prothrombin Conversion

Bovine Factor V isolated by the method of Esnouf and Jobin (1967) has been further purified by affiniy chromotgraphy through prothrombin-sepharose. Factor V bound quantitative to the prothrombin-sepharose column. There was a 2-fold increase in the average specific activity (260.000 units/mg protein) of the Factor V recovered. Recovery of total Factor V activity and total protein was about 95% and 90% respectively.

Production and purification of constructed recombinant hirudin in BL21(DE3) strain

Background/Objective: Hirudin, an extract from the leech, has powerful antithrombin activity affecting the blood coagulation pathway, it is the most potent natural inhibitor of thrombin, it binds thrombin with high affinity, so, the aim of this study was to build hirudin gene by overlapping extension PCR then cloning and expression in BL21(DE3) strain.Methods: Hirudin gene constructed with four modified primers then the final product amplified by two primers named as A, B by using overlapping extension PCR, for gene expression, BL21(DE3) strain was used under the control of T7 promoter in pET-16b vector and for hirudin production, LB broth medium was used as fermentation medium. Hirudin protein purified at first by (Immobilized metal affinity chromatography) IMAC, then this protein was dialysis and treated with factor Xa to eliminate His-tag. Then hirudin purified by DEAE sepharose and SP sepharose column, the concentration of protein determined by ELISA, furthermore the activity evaluated by thrombin titration and activated partial thromboplastin time (APPT) test.Results: Hirudin gene constructed in two round PCR first round produced two products (product1 117 bp while product 2,114 bp) the second-round PCR gave the final product 213 bp. The resulted band from gel electrophoresis for constructed vector pET-16b-HirudinS was (5,901 bp). The analysis on 15% SDS-PAGE for the SP sepharose column illustrated the hirudinS protein band with size about ~10.8. Concentration of produced hirudin within its solution reached to 1.75 ng, thrombin titration method showed that the hirudin protein required 300 µl from thrombin to clot, also, APPT test showed that hirudin elongated clotting time to 7min in comparison with 6min for aspirin and the statistical analysis results for APPT test illustrated that there was no significant difference between hirudin and aspirin.Conclusion: This study approved that overlapping extension PCR is a good strategy for building hirudin gene and it’s successfully expressed in BL21(DE3) strain.

Optimization, Purification, and Starch Stain Wash Application of Two Newα-Amylases Extracted from Leaves and Stems ofPergularia tomentosa

A continuous research is attempted to fulfil the highest industrial demands of natural amylases presenting special properties. Newα-amylases extracted from stems and leaves ofPergularia tomentosa, which is widespread and growing spontaneously in Tunisia, were studied by the means of their activities optimization and purification. Some similarities were recorded for the two identified enzymes: (i) the highest amylase activity showed a promoted thermal stability at 50°C; (ii) the starch substrate at 1% enhanced the enzyme activity; (iii) the twoα-amylases seem to be calcium-independent; (iv) Zn2+, Cu2+, and Ag2+were considered as important inhibitors of the enzyme activity. Following the increased gradient of elution on Mono Q-Sepharose column, an increase in the specific activity of 11.82-fold and 10.92-fold was recorded, respectively, for leaves and stems with the presence of different peaks on the purification profiles.Pergulariaamylases activities were stable and compatible with the tested commercial detergents. The combination of plant amylase and detergent allowed us to enhance the wash performance with an increase of 35.24 and 42.56%, respectively, for stems and leaves amylases. Characterized amylases were reported to have a promoted potential for their implication notably in detergent industry as well as biotechnological sector.

Polygalacturonase and xylanase forms produced by Fusarium avenaceum in infected lupin roots and their sensitivity to a cell wall glycoprotein

Using CM-Sepharose column chromatography it was shown that <em>Fusarium avenaceum</em> produced two forms of endo-polygalacturonase, one exo-polygalacturonase and two forms of endo-xylanase in infected Iupin roots. A glycoprotein obtained from lupin seedlings inhibited endo-polygalacturonases, exo-polygalacturonases and xylanases but more the first ones. Two forms of endo-polygalacturonase did not differ in their sensitivity to the glycoprotein.

Production of Bacteriocin E50-52 by Small Ubiquitin-Related Modifier Fusion in Escherichia coli

Bacteriocin E50-52, a class IIa bacteriocin with a wide antibacterial spectrum, and has a huge potential to be a substitute for convention. antibiotics. In this research, the bacteriocin E50-52 gene was cloned into the expression vector pET SUMO (small ubiquitin-related modifier) and introduced into Escherichia coli BL21 (DE3). The recombinant fusion protein SUMO-bacteriocin E50-52 expressed in a soluble form was purified to a purity of more than 90% by Ni-NTA sepharose column and 117 mg fusion protein was obtained per liter of fermentation culture. The fusion protein was cleaved with SUMO protease and re-applied to a Ni-NTA Sepharose column. Finally, about 16 mg recombinant bacteriocin E50-52 (rbE50-52) was obtained from a 1-liter fermentation culture with no less than 95% purity. The rbE50-52 had similar antimicrobial properties and molecular weight as the native bacteriocin E50-52 and showed very low hemolytic activity.

The ferric aerobactin receptor IutA, a protein isolated on agarose column, is not essential for uropathogenic Escherichia coli infection

Although many proteins have been described involved in Escherichia coli colonization and infection, only few reports have shown lectins as important components in these processes. Because the mechanisms underlying E. coli colonization process involving lectins are not fully understood, we sought to identify the presence of other non-described lectins in E. coli. Here, we isolated a 75-kDa protein from E. coli on Sepharose column and identified it as ferric aerobactin receptor (IutA). Since IutA is controversially associated with virulence of some E. coli strains, mainly in uropathogenic E. coli (UPEC), we evaluated the presence of iutA gene in UPEC isolated from patients with urinary infection. This gene was present in only 38% of the isolates, suggesting a weak association with virulence. Because there is a redundancy in the siderophore-mediated uptake systems, we suggest that IutA can be advantageous but not essential for UPEC.