L-Asparaginases (E.C. are group of enzymes which catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia. Many microorganisms are known to produce two types of L-asparaginase. Considerable attention has been specifically drawn to type II L-asparaginases due to their potent tumor-inhibitory activity. Various limitations, such as high toxicity, poor stability and short half-life, are associated with the commercially available L-asparaginases used in cancer therapy. Additionally, L-asparaginases have a significant role in food industry owing to their ability to reduce the levels of acrylamide, which is a known neurotoxin and a potential carcinogen, in various food products. Knowing that less than 1% of microorganisms can be detected using standard culturing techniques, searching for new L-asparaginases II with improved properties using metagenomic approaches seems promising. The metagenomes of extreme environments serve as a potential source for novel biomolecules that can, in most cases, function optimally under the extreme conditions of their environments. Having a temperature of 68°C, salinity of 250 parts per thousand, high concentrations of heavy metals and very low oxygen levels, the lower convective layer (LCL) of the Atlantis II brine pool (ATII) in the Red Sea is considered one of the harshest marine environments, and hence an attractive site for mining for a novel L-asparaginase II. Several studies successfully isolated different L-asparaginases II from cultured isolates, however, to the best of our knowledge, this is the first study to isolate and characterize L-asparaginase II using metagenomic approach. In this study, a putative L-asparaginase II (AspATII) was identified through computational analysis of the ATII-LCL metagenomic database. The environmental DNA of the LCL was screened for the identified gene using sequence-based approach. Amplified genes were cloned into pET 20b(+) expression vectors, while pET-22b(+) vectors were used to express codon optimized genes. Protein expression was carried out in Escherichia coli (E.coli) BL21 (DE3) cells and the His-tagged protein was purified from the culture medium of cells transformed with recombinant pET 22b(+) vectors. Characterization of the purified protein revealed that it is a thermostable (optimum temperature, 50°C), halotolerant (maintains its activity up to 4 M NaCl) L- asparaginase II, which makes it highly beneficial for various biotechnological and industrial applications.


School of Sciences and Engineering

Degree Name

MS in Biotechnology

First Advisor

Moustafa, Ahmed

Second Advisor

Ferreira, Ari Jose

Third Advisor

Abou-Aisha, Khaled

Committee Member 1

Fouad, Walid

Committee Member 2

Abdel Latif, Ahmed

Committee Member 3

Moustafa, Ahmed

Document Type



The American University in Cairo grants authors of theses and dissertations a maximum embargo period of two years from the date of submission, upon request. After the embargo elapses, these documents are made available publicly. If you are the author of this thesis or dissertation, and would like to request an exceptional extension of the embargo period, please write to thesisadmin@aucegypt.edu