Production and Purification of Therapeutic Enzymes

A critical review on exploitation of agro-industrial biomass as substrates for the therapeutic microbial enzymes production and implemented protein purification techniques

Annually, a huge amount of waste is generated by the industries that use agricultural biomass. Researchers have looked into employing this cheap and renewable agro-biomass as a substrate for enzyme production via fermentation processes to meet the ever-increasing worldwide need. Although there are a number of sources for enzyme extraction, microbial sources have dominated industrial sectors due to their easy availability and rapid growth. Microbial enzymes are currently used in a variety of industries, including pharmaceuticals, food, biofuels, textiles, paper, detergents, and so on, and using these nutritious feedstocks not only reduces production costs but also helps to reduce environmental concerns. The present review focuses on the therapeutic microbial enzymes produced using different agro-industrial biomass as raw materials, with down-streaming techniques for obtaining a final pure product. Additionally, the article also discussed biomass pretreatment processes, including physical, chemical and biological. The type of pretreatment method to be used is mostly governed by the intended use of the major molecular components of biomass (cellulose, hemicelluloses and lignin). Finally, purification challenges are included. All of this information will be useful in the industrial synthesis of high-purity targeted enzymes if the crucial aspects that have been discussed are taken into account.

Liposomes as Tools to Improve Therapeutic Enzyme Performance

The drugs concept has changed during the last few decades, meaning the acceptance of not only low molecular weight entities but also macromolecules as bioagent constituents of pharmaceutics. This has opened a new era for a different class of molecules, namely proteins in general and enzymes in particular. The use of enzymes as therapeutics has posed new challenges in terms of delivery and the need for appropriate carrier systems. In this review, we will focus on enzymes with therapeutic properties and their applications, listing some that reached the pharmaceutical market. Problems associated with their clinical use and nanotechnological strategies to solve some of their drawbacks (i.e., immunogenic reactions and low circulation time) will be addressed. Drug delivery systems will be discussed, with special attention being paid to liposomes, the most well-studied and suitable nanosystem for enzyme delivery in vivo. Examples of liposomal enzymatic formulations under development will be described and successful pre-clinical results of two enzymes, L-Asparaginase and Superoxide dismutase, following their association with liposomes will be extensively discussed.

Kinetic and pharmacokinetic characteristics of therapeutic methinoninе γ-lyase encapsulated in polyion complex vesicles

Therapeutic enzymes used for the treatment of a wide range of human disorders often suffer from suboptimal pharmacokinetics and stability. Engineering approaches such as encapsulation in micro- and nanocarriers, and replacements of amino acid residues of the native enzyme provide significant potential for improving the performance of enzyme therapy. Here, we develop a nanodelivery system on the base of polyion complex vesicles (PICsomes) that includes methionine γ-lyase (MGL) as a therapeutic enzyme. We have two strategies for using the enzyme: first, methionine γ-lyase is an anticancer agent removing l-methionine from plasma, second, the binary system methionine γ-lyase/S-alk(en)yl-l-cysteine sulfoxides is effective in enzyme prodrug therapy (EPT). Various lengths polymers were synthesized, and two mutant forms of the enzyme were used. The catalytic and pharmacokinetic parameters of the nanoformulations were investigated. The catalytic efficiencies of encapsulated enzymes were comparable to that of native enzymes. Pharmacokinetic analysis has shown that inclusion into PICsomes increases half-life of the enzymes, and they can be safely administered in vivo. The results suggest the further use of encapsulated MGLs for EPT and anticancer therapy, and this strategy could be leveraged to improve the efficiency of enzyme-based therapies for managing serious human diseases.

Enhanced clot lysis by a single point mutation in a reteplase variant

Recombinant tissue-type plasminogen activator (rtPA) is the clot lysis drug approved for clinical use, and is characterised by a short half-life and substantial inactivation by plasminogen activator inhibitor-1 (PAI-1). We previously discovered that a tPA mutation (A419Y) at the protease domain led to enhanced fibrinolysis activity. In the present study, we studied the mechanism of such mutation in enhancing the proteolytic activity, and whether such enhancement persists in reteplase, an United States Food and Drug Administration-approved tPA truncated variant. We constructed and expressed a series of reteplase-based mutants, including rPA^G (glycosylated rPA), rPA^G -Y (with A419Y mutant at rPA^G ), rPA^G -A4 (tetra-alanine mutation at 37-loop of rPA^G ), and rPA^G -A4/Y (with both) and evaluated their plasminogen activation and PAI-1 resistance. Surface plasmon resonance analysis showed that the rPA^G had fibrin affinity comparable to full-length tPA. Moreover, rPA^G -Y had 8·5-fold higher plasminogen activation and stronger tolerance to PAI-1 compared to rPA^G . We also found that the mutations containing tetra-alanine (rPA^G -A4 and rPA^G -A4/Y) had dramatically reduced plasminogen activation and impaired clot lysis. In a pulmonary embolism murine model, rPA^G -Y displayed a more efficient thrombolytic effect than rPA^G . These results identified a novel mutant reteplase variant of tPA with increased fibrinolytic activity, laying the foundation for the development of a new potent fibrinolytic agent.

Impact of lipopolysaccharides on cultivation and recombinant protein expression in human embryonal kidney (HEK-293) cells

The human embryonal kidney 293 cell (HEK-293) is a widely used expression host for transient gene expression. The genes or plasmids used for the transient transfections are usually propagated and extracted from the gram-negative bacterium Escherichia coli, the workhorse for molecular biologists. As a gram-negative bacterium E. coli has an outer membrane (OM) containing lipopolysaccharides (LPS) or endotoxins. LPS are very potent inducers of inflammatory cytokines in the body. In early research phases DNA intended for transient transfections is not routinely checked for LPS-levels. In this study we addressed the question whether LPS has an impact on the cultivation and production of a recombinant antibody. At high concentrations the presence of LPS has a detrimental impact on cell viability and recombinant protein expression. But low LPS concentrations are tolerated and might even enhance protein expression levels.

Virus-Derived Peptides for Hepatic Enzyme Delivery

Recently, a lipopeptide derived from the hepatitis B virus (HBV) large surface protein has been developed as an HBV entry inhibitor. This lipopeptide, called MyrcludexB (MyrB), selectively binds to the sodium taurocholate cotransporting polypeptide (NTCP) on the basolateral membrane of hepatocytes. Here, the feasibility of coupling therapeutic enzymes to MyrB was investigated for the development of enzyme delivery strategies. Hepatotropic targeting shall enable enzyme prodrug therapies and detoxification procedures. Here, horseradish peroxidase (HRP) was conjugated to MyrB via maleimide chemistry, and coupling was validated by SDS-PAGE and reversed-phase HPLC. The specificity of the target recognition of HRP-MyrB could be shown in an NTCP-overexpressing liver parenchymal cell line, as demonstrated by competitive inhibition with an excess of free MyrB and displayed a strong linear dependency on the applied HRP-MyrB concentration. In vivo studies in zebrafish embryos revealed a dominating interaction of HRP-MyrB with scavenger endothelial cells vs xenografted NTCP expressing mammalian cells. In mice, radiolabeled ¹²⁵I-HRP-MyrBy, as well as the non-NTCP targeted control HRP-peptide-construct (¹²⁵I-HRP-alaMyrBy) demonstrated a strong liver accumulation confirming the nonspecific interaction with scavenger cells. Still, MyrB conjugation to HRP resulted in an increased and NTCP-mediated hepatotropism, as revealed by competitive inhibition. In conclusion, the model enzyme HRP was successfully conjugated to MyrB to achieve NTCP-specific targeting in vitro with the potential for ex vivo diagnostic applications. In vivo, target specificity was reduced by non-NTCP-mediated interactions. Nonetheless, tissue distribution experiments in zebrafish embryos provide mechanistic insight into underlying scavenging processes indicating partial involvement of stabilin receptors.

Protein Purification Technologies

Protein Biotechnology is an exciting and fast- growing area of research, with numerous industrial applications. The growing demand for developing efficient and rapid protein purification methods is driving research and growth in this area. Advances and progress in the techniques and methods of protein purification have been such that one can reasonably expect that any protein of a given order of stability may be purified to currently acceptable standards of homogeneity. However, protein manufacturing cost remains extremely high, with downstream processing constituting a substantial proportion of the overall cost. Understanding of the methods and optimization of the experimental conditions have become critical to the manufacturing industry in order to minimize production costs while satisfying the quality as well as all regulatory requirements. New purification processes exploiting specific, effective and robust methods and chromatographic materials are expected to guide the future of the protein purification market.

Animal Model Contributions to Congenital Metabolic Disease

Genetic model systems allow researchers to probe and decipher aspects of human disease, and animal models of disease are frequently specifically engineered and have been identified serendipitously as well. Animal models are useful for probing the etiology and pathophysiology of disease and are critical for effective discovery and development of novel therapeutics for rare diseases. Here we review the impact of animal model organism research in three examples of congenital metabolic disorders to highlight distinct advantages of model system research. First, we discuss phenylketonuria research where a wide variety of research fields and models came together to make impressive progress and where a nearly ideal mouse model has been central to therapeutic advancements. Second, we review advancements in Lesch-Nyhan syndrome research to illustrate the role of models that do not perfectly recapitulate human disease as well as the need for multiple models of the same disease to fully investigate human disease aspects. Finally, we highlight research on the GM2 gangliosidoses Tay-Sachs and Sandhoff disease to illustrate the important role of both engineered traditional laboratory animal models and serendipitously identified atypical models in congenital metabolic disorder research. We close with perspectives for the future for animal model research in congenital metabolic disorders.