Enhancement of the solubility and stability of D-amino acid oxidase by fusion to an elastin like polypeptide

Coupling a recombinant oxidase to catalase through specific noncovalent interaction to improve the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

5-Hydroxymethylfurfural oxidase (HMFO) can catalyze both hydroxyl and aldehyde oxidations. It catalyzes 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid. However, the application of HMFO encountered two problems: the expressed HMFO in Escherichia coli. is largely in the form of inclusion bodies, and the by-product of H₂O₂ has a negative effect on HMFO stability. To solve these problems, recombinant HMFO was generated by fusing the C-terminus to an elastin-like polypeptide (ELP). ELP-HMFO can be expressed with significantly reduced inclusion bodies. ELP-HMFO exhibited improved stability and tolerance toward H₂O₂. Further recombination is carried out by fusing the N-terminus of HMFO to a glutamic acid-rich leucine zipper motif (Z_E). Similarly, recombinant catalase (CAT) is generated by fusing the N-terminus to ELP and fusing the C-terminus to an arginine-rich leucine zipper motif (Z_R). ELP-HMFO-Z_E can interact specifically with Z_R-CAT-ELP, ascribing to the coiled-coil association of Z_E and Z_R. ELP-HMFO-Z_E#Z_R-CAT-ELP coordinates the respective catalytic activities of the two enzymes. ELP-HMFO-Z_E catalyzes the oxidation of HMF, and the generated hydrogen peroxide is decomposed by Z_R-CAT-ELP into H₂O and oxygen. During the oxidation of HMF, the cofactor FAD of HMFO is reduced, and molecular oxygen is needed to reoxidize the reduced FAD. The evolved oxygen from the decomposing of H₂O₂ can just meet the requirement, which can be diffused efficiently from Z_R-CAT-ELP to ELP-HMFO-Z_E due to the short distance between the two enzymes.

Fabrication of a Fibrous Metal-Organic Framework and Simultaneous Immobilization of Enzymes

A nanorod-like lanthanum metal-organic framework (LaMOF) was synthesized in aqueous solution by coordinating La(III) to the ligand 1,3,5-benzenetricarboxylic acid. The fibrous LaMOF was fabricated by splitting the nanorod-like LaMOF in a solution of d-amino acid oxidase, and the enzyme was immobilized simultaneously. Based on SEM and TEM images, STEM mapping, and spectra of XPS and FTIR, the mechanism of formation of the fibrous LaMOF and the distinct interfacial phenomena have been elucidated. The fabrication of the fibrous LaMOF and simultaneous immobilization of the enzyme were carried out in aqueous solutions at room temperature, without using any organic solvent. It is a clean and time- and energy-effective process. This work presents a distinct and clean methodology for the fabrication of the fibrous MOF. Potentially, the environmentally benign methodology can be extended to immobilize other enzymes.

Utilizing a Kidney-Targeting Peptide to Improve Renal Deposition of a Pro-Angiogenic Protein Biopolymer

Elastin-like polypeptides (ELP) are versatile protein biopolymers used in drug delivery due to their modular nature, allowing fusion of therapeutics and targeting agents. We previously developed an ELP fusion with vascular endothelial growth factor (VEGF) and demonstrated its therapeutic efficacy in translational swine models of renovascular disease and chronic kidney disease. The goal of the current work was to refine renal targeting and reduce off-target tissue deposition of ELP–VEGF. The ELP–VEGF fusion protein was modified by adding a kidney-targeting peptide (KTP) to the N-terminus. All control proteins (ELP, KTP–ELP, ELP–VEGF, and KTP–ELP–VEGF) were also produced to thoroughly assess the effects of each domain on in vitro cell binding and activity and in vivo pharmacokinetics and biodistribution. KTP–ELP–VEGF was equipotent to ELP–VEGF and free VEGF in vitro in the stimulation of primary glomerular microvascular endothelial cell proliferation, tube formation, and extracellular matrix invasion. The contribution of each region of the KTP–ELP–VEGF protein to the cell binding specificity was assayed in primary human renal endothelial cells, tubular epithelial cells, and podocytes, demonstrating that the VEGF domain induced binding to endothelial cells and the KTP domain increased binding to all renal cell types. The pharmacokinetics and biodistribution of KTP–ELP–VEGF and all control proteins were determined in SKH-1 Elite hairless mice. The addition of KTP to ELP slowed its in vivo clearance and increased its renal deposition. Furthermore, addition of KTP redirected ELP–VEGF, which was found at high levels in the liver, to the kidney. Intrarenal histology showed similar distribution of all proteins, with high levels in blood vessels and tubules. The VEGF-containing proteins also accumulated in punctate foci in the glomeruli. These studies provide a thorough characterization of the effects of a kidney-targeting peptide and an active cytokine on the biodistribution of these novel biologics. Furthermore, they demonstrate that renal specificity of a proven therapeutic can be improved using a targeting peptide.

Efficient production of d-amino acid oxidase in Escherichia coli by a trade-off between its expression and biomass using N-terminal modification

Native d-amino acid oxidase (DAAO) that is expressed mostly as inclusion body and its toxicity for E. coli hamper efficient heterologous expression. In this study, the soluble expression of DAAO from Rhodosporidium toruloides (RtDAAO) was improved in E. coli through N-terminal modification, but the cell biomass was decreased. Then a trade-off between DAAO expression and biomass was achieved to obtain the highest volumetric activity of DAAO through regulated the number of N-terminus histidine residues. When variant ²H³G was fused with three N-terminus histidine residues, the volumetric activity was increased by 3.1 times and the biomass was not significant change compared with the wild type. Finally, the N-terminus disordered region of RtDAAO (HSQK) was replaced with HHHG and the variant enzyme activity reached 80.7U/mL (with a 40 percent of inactive DAAO reduced) in a 7.5L fermenter in 24h.

Elastin-like polypeptides: Therapeutic applications for an emerging class of nanomedicines

Elastin-like polypeptides (ELPs) constitute a genetically engineered class of 'protein polymers' derived from human tropoelastin. They exhibit a reversible phase separation whereby samples remain soluble below a transition temperature (Tt) but form amorphous coacervates above Tt. Their phase behavior has many possible applications in purification, sensing, activation, and nanoassembly. As humanized polypeptides, they are non-immunogenic, substrates for proteolytic biodegradation, and can be decorated with pharmacologically active peptides, proteins, and small molecules. Recombinant synthesis additionally allows precise control over ELP architecture and molecular weight, resulting in protein polymers with uniform physicochemical properties suited to the design of multifunctional biologics. As such, ELPs have been employed for various uses including as anti-cancer agents, ocular drug delivery vehicles, and protein trafficking modulators. This review aims to offer the reader a catalogue of ELPs, their various applications, and potential for commercialization across a broad spectrum of fields.