Nada Anwar Abdelrazek Hegazy

Mahmoud Eissa;;Marwa Saady

31/12/2022

https://pubmed.ncbi.nlm.nih.gov/36585987/

Nada Anwar Abdelrazek Hegazy

Walid F. Elkhatib , Marwa M. Raafat and Mohammad M. Aboulwafa

01/04/2020

An exhaustive screening program was applied for scoring a promising l-asparaginase producing-isolate. The recov ered isolate was identifed biochemically and molecularly and its l-asparaginase productivity was optimized experi mentally and by Response Surface Methodology. The produced enzyme was characterized experimentally for its cata lytic properties and by bioinformatics analysis for its immunogenicity. The promising l-asparaginase producing-isolate was selected from 722 recovered isolates and identifed as Stenotrophomonas maltophilia and deposited at Microbio logical Resources Centre (Cairo Mircen) under the code EMCC2297. This isolate produces both intracellular (type I) and extracellular (type II) l-asparaginases with about 4.7 fold higher extracellular l-asparaginase productivity. Bioinformat ics analysis revealed clustering of Stenotrophomonas maltophilia l-asparaginase with those of Pseudomonas species and considerable closeness to the two commercially available l-asparaginases of E. coli and Erwinia chrysanthemi. Fourteen antigenic regions are predicted for Stenotrophomonas maltophilia l-asparaginase versus 16 and 18 antigenic regions for the Erwinia chrysanthemi and E. coli l-asparaginases. Type II l-asparaginase productivity of the test isolate reached 4.7 IU/ml/h and exhibited maximum activity with no metal ion requirement at 37 °C, pH 8.6, 40 mM aspara gine concentration and could tolerate NaCl concentration up to 500 mM and retain residual activity of 55% at 70 °C after half an hour treatment period. Application both of random mutation by gamma irradiation and Response Sur face Methodology that determined 38.11 °C, 6.89 pH, 19.85 h and 179.15 rpm as optimum process parameters could improve the isolate l-asparaginase productivity. Maximum production of about 8 IU/ml/h was obtained with 0.4% dextrose, 0.1% yeast extract and 10 mM magnesium sulphate. In conclusion l-asparaginase of the recovered Steno trophomonas maltophilia EMCC2297 isolate has characters enabling it to be used for medical therapeutic application

Nada Anwar Abdelrazek Hegazy

Walid Faisal Elkhatib, Mohammad Aboulwafa

01/04/2019

L-asparaginase, also known as amidohydrolase, catalyzes the breakdown of asparagine into aspartic acid and ammonia. Due to its ability to inhibit the biosynthesis of protein lymphoblasts, it is used to treat acute lymphoblastic leukemia (ALL). It also has other applications in the food industry by preventing the formation of acrylamide. Different organisms including bacteria, fungi, actinomycetes, and plants produce L-asparaginase. This review highlights different applications of L-asparaginase in the industrial fields, the major sources of L-asparaginase, its immunological reactions and production techniques through the solid state (SSF) and submerged (SmF) fermentation as well as optimization of the production process.

Nada Anwar Abdelrazek Hegazy

Walid F. Elkhatib, Mohammad M. Aboulwafa

01/03/2019

A Bacillus licheniformis isolate with high L-asparaginase productivity was recovered upon screening two hundred soil samples. This isolate produces the two types of bacterial L-asparaginases, the intracellular type I and the extracellular type II. The catalytic activity of type II enzyme was much higher than that of type I and reached about 5.5 IU/ml/h. Bioinformatics analysis revealed that L-asparaginases of Bacillus licheniformis is clustered with those of Bacillus subtilis, Bacillus haloterans, Bacillus mojavensis and Bacillus tequilensis while it exhibits distant relatedness to L-asparaginases of other Bacillus subtilis species as well as to those of Bacillus amyloliquefaciens and Bacillus velezensis species. Upon comparison of Bacillus licheniformis L-asparaginase to those of the two FDA approved L-asparaginases of E. coli (marketed as Elspar) and Erwinia chrysanthemi (marketed as Erwinaze), it observed in a cluster distinct from- and with validly predicted antigenic regions number comparable to those of the two mentioned reference strains. It exhibited maximum activity at 40 °C, pH 8.6, 40 mM asparagine, 10 mM zinc sulphate and could withstand 500 mM NaCl and retain 70% of its activity at 70 °C for 30 min exposure time. Isolate enzyme productivity was improved by gamma irradiation and optimized by RSM experimental design (Box–Behnken central composite design). The optimum conditions for maximum L-asparaginase production by the improved mutant were 39.57 °C, 7.39 pH, 20.74 h, 196.40 rpm, 0.5% glucose, 0.1% ammonium chloride, and 10 mM magnesium sulphate. Taken together, Bacillus licheniformis L-asparaginase can be considered as a promising candidate for clinical application as antileukemic agent