Engineering resistance to trypsin inactivation into L-asparaginase through the production of a chimeric protein between the enzyme and a protective single-chain antibody

In Silico Design of a Chimeric Humanized L-asparaginase

Acute lymphoblastic leukemia (ALL) is the most common cancer among children worldwide, characterized by an overproduction of undifferentiated lymphoblasts in the bone marrow. The treatment of choice for this disease is the enzyme L-asparaginase (ASNase) from bacterial sources. ASNase hydrolyzes circulating L-asparagine in plasma, leading to starvation of leukemic cells. The ASNase formulations of E. coli and E. chrysanthemi present notorious adverse effects, especially the immunogenicity they generate, which undermine both their effectiveness as drugs and patient safety. In this study, we developed a humanized chimeric enzyme from E. coli L-asparaginase which would reduce the immunological problems associated with current L-asparaginase therapy. For these, the immunogenic epitopes of E. coli L-asparaginase (PDB: 3ECA) were determined and replaced with those of the less immunogenic Homo sapiens asparaginase (PDB:4O0H). The structures were modeled using the Pymol software and the chimeric enzyme was modeled using the SWISS-MODEL service. A humanized chimeric enzyme with four subunits similar to the template structure was obtained, and the presence of asparaginase enzymatic activity was predicted by protein-ligand docking.

Molecular Analysis of L-Asparaginases for Clarification of the Mechanism of Action and Optimization of Pharmacological Functions

L-asparaginases (EC 3.5.1.1) are a family of enzymes that catalyze the hydrolysis of L-asparagine to L-aspartic acid and ammonia. These proteins with different biochemical, physicochemical and pharmacological properties are found in many organisms, including bacteria, fungi, algae, plants and mammals. To date, asparaginases from E. coli and Dickeya dadantii (formerly known as Erwinia chrysanthemi) are widely used in hematology for the treatment of lymphoblastic leukemias. However, their medical use is limited by side effects associated with the ability of these enzymes to hydrolyze L-glutamine, as well as the development of immune reactions. To solve these issues, gene-editing methods to introduce amino-acid substitutions of the enzyme are implemented. In this review, we focused on molecular analysis of the mechanism of enzyme action and to optimize the antitumor activity.

A critical review on properties and applications of microbial l-asparaginases

l-Asparaginase is one of the main drugs used in the treatment of acute lymphoblastic leukemia (ALL), a commonly diagnosed pediatric cancer. Although several microorganisms are found to produce l-asparaginase, only the purified enzymes from E. coli and Erwinia chrysanthemi are employed in the clinical and therapeutic applications in humans. However, their therapeutic response seldom occurs without some evidence of hypersensitivity and other toxic side effects. l-Asparaginase is also of prospective use in food industry to reduce the formation of acrylamide in fried, roasted or baked food products. This review is an attempt to compile information on the properties of l-asparaginases obtained from different microorganisms. The complications involved with the therapeutic use of the currently available l-asparaginases, and the enzyme's potential application as a food processing aid to mitigate acrylamide formation have also been reviewed. Further, avenues for searching alternate sources of l-asparaginase have been discussed, highlighting the prospects of endophytic microorganisms as a possible source of l-asparaginases with varied biochemical and pharmacological properties.

L-Asparaginase: A Promising Chemotherapeutic Agent

This article comprises detailed information about L-asparaginase, encompassing topics such as microbial and plant sources of L-asparaginase, treatment with L-asparaginase, mechanism of action of L-asparaginase, production, purification, properties, expression and characteristics of l-asparaginase along with information about studies on the structure of L-asparaginase. Although L-asparaginase has been reviewed by Savitri and Azmi (2003), our effort has been to include recent and updated information about the enzyme covering new aspects such as structural modification and immobilization of L-asparaginase, recombinant L-asparaginase, resistance to L-asparaginase, methods of assay of L-asparagine and L-asparaginase activity using the biosensor approach, L-asparaginase activity in soil and the factors affecting it. Also, side-effects of L-asparaginase treatment in acute lymphoblastic leukemia (ALL) have been discussed in the current review. L-asparaginase has been and is still one of the most widely studied therapeutic enzymes by researchers and scientists worldwide.

Hydrophobic interactions are the prevalent force in bromelain:Fab’ complex

Antibromelain polyclonal antibodies against stem bromelain were raised in male albino rabbits and the Fab monomers isolated from the IgG of the immune sera as reported in our earlier communication (Gupta, P., Khan, R. H., and Saleemuddin, M. (2003) Biochim. Biophys. Acta, 1646, 131-135). Further, as evident from that communication bromelain:Fab complex has 1 : 1 stoichiometry. The stability of bromelain:Fab complex (1 : 1 stoichiometry) was investigated by far and near-UV CD and fluorescence measurements. Addition of up to 1.8 M NaCl caused no significant changes in fluorescence signals and near-UV CD peak pattern. However, the spectral studies together with gel filtration studies suggest dissociation of the complex beyond 5% (v/v) methanol. These results show that hydrophobic interactions play a pronounced role in the binding of Fab to bromelain while electrostatic interactions may be less crucial.

Construction of proteolysis resistant human interleukin-2 by fusion to its protective single chain antibody

Interleukin-2 (IL-2) is a 15 kDa cytokine secreted by T-cells. Consequence to its natural function as locally secreted short-term messenger, its half-life in circulation is short and provided mainly by fast renal clearance due to its low molecular weight and its proteolytic susceptibility. These are common characteristics for most cytokines, resulting in low clinical utility. In this study we report the construction of an IL-2 fusion-protein comprising a protective anti-hIL-2 single chain antibody that was selected from a phage display library and the hIL-2. This IL-2 fusion-protein is fully human and resistant to inactivation by the ubiquitous lysosomal protease-cathepsin D, which is implicated in the in vivo inactivation of IL-2. In contrast, the native IL-2 lost practically all of its activity under these conditions. This resistance is due to the interaction of the single chain domain with its epitope on IL-2 thus masking possible cleavage sites. We suggest that this 45 kDa proteolysis resistant IL-2 fusion-protein upon further increase of its molecular weight by common fusion techniques to at least 75 kDa will exhibit significantly longer half-life in vivo and a higher clinical utility than either the native IL-2 or any of its reported long T/2 derivatives.

Bioaffinity based immobilization of enzymes

Procedures that utilize the affinities of biomolecules and ligands for the immobilization of enzymes are gaining increasing acceptance in the construction of sensitive enzyme-based analytical devices as well as for other applications. The strong affinity of polyclonal/monoclonal antibodies for specific enzymes and those of lectins for glycoenzymes bearing appropriate oligosaccharides have been generally employed for the purpose. Potential of affinity pairs like cellulose-cellulose binding domain bearing enzymes and immobilized metal ionsurface histidine bearing enzymes has also been recognised. The bioaffinity based immobilization procedures usually yield preparations exhibiting high catalytic activity and improved stability against denaturation. Bioaffinity based immobilizations are usually reversible facilitating the reuse of support matrix, orient the enzymes favourably and offer the possibility of enzyme immobilization directly from partially pure enzyme preparations or even cell lysates. Enzyme lacking innate ability to bind to various affinity supports can be made to bind to them by chemically or genetically linking the enzymes with appropriate polypeptides/domains like the cellulose binding domain, protein A, histidine-rich peptides, single chain antibodies, etc.