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    Membrane permeabilization of gram-negative bacteria with a potassium phosphate/hexane aqueous phase system for the release of L-asparaginase: an enzyme used in cancer therapy
    (Elsevier Sci Ltd, 2005) Geckil, H; Ates, B; Gencer, S; Uckun, M; Yilmaz, I
    A fast, efficient and reproducible recovery procedure for periplasmic L-asparaginase from two distinctly related gram-negative bacteria, Enterobacter aerogenes and Pseudomonas aeruginosa, is presented. As the method uses inexpensive organic solvent hexane and an aqueous salt solution, it is also highly cost-effective in comparison with the currently available techniques used for the release of this enzyme. As hexane is a highly water immiscible organic solvent, it can be removed easily from the top of the aqueous phase by a simple evaporation. Also, various organic solvents and other membrane partitioning compounds were compared for their efficiency on L-asparaginase/protein release. The degree to which the enzyme was released was different for two bacteria, suggesting that they possess different permeability characteristics. The most efficient enzyme release from both bacteria was determined to be in 50 mM potassium phosphate with 1% hexane. Enzyme recoveries up to three-fold with respect to sonication have been achieved with this system. (C) 2004 Elsevier Ltd. All rights reserved.
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    Vitreoscilla hemoglobin expressing Enterobacter aerogenes and Pseudomonas aeruginosa respond differently to carbon catabolite and oxygen repression for production of L-asparaginase, an enzyme used in cancer therapy
    (Elsevier Science Inc, 2004) Geckil, H; Gencer, S; Uckun, M
    The production of antileukemic enzyme L-asparaginase in two distinctly related bacteria, Enterobacter aerogenes, Pseudomonas aeruginosa, and in their recombinants expressing the Vitresocilla hemoglobin (VHb) has been studied. Both bacteria showed a substantially different degree of carbon catabolite repression of the enzyme production. E. aerogenes grown under catabolite repression had more than 20-fold lower L-asparaginase activity than the controls. This figure was only 1.6-fold for P. aeruginosa. In the medium with restricted nutrient content, however, the inhibitory effect of glucose on the enzyme production was less pronounced. The presence of VHb, an efficient oxygen uptake system, had also different effects in both bacteria. Under conditions of no catabolite repression, this protein caused about 7-fold lower L-asparaginase activity in E. aerogenes, but similar or even slightly stimulatory effect in P aeruginosa. The use of a relatively poor carbon source, mannitol, caused a lower L-asparaginase level and no glucose type catabolite repression. (C) 2004 Elsevier Inc. All rights reserved.