Uricase Research Articles

Chemical Modification of Cysteine with 3-Arylpropriolonitrile Improves the In Vivo Stability of Albumin-Conjugated Urate Oxidase Therapeutic Protein.

3-arylpropiolonitriles (APN) are promising alternatives to maleimide for chemo-selective thiol conjugation, because the reaction product has a remarkably hydrolytic stability compared with that of thiol-maleimide reactions in vitro. However, whether cysteine modification with APN enhances stability in vivo compared to thiol-maleimide reactions remains unclear, probably due to the too short in vivo serum half-life of a protein to observe significant cleavage of thiol-maleimide/-APN reaction products. The conjugation of human serum albumin (HSA) to a therapeutic protein reportedly prolongs the in vivo serum half-life. To evaluate the in vivo stability of the thiol-APN reaction product, we prepared HSA-conjugated Arthrobacter globiformis urate oxidase (AgUox), a therapeutic protein for gout treatment. Site-specific HSA conjugation to AgUox was achieved by combining site-specific incorporation of tetrazine containing an amino acid (frTet) into AgUox and a crosslinker containing trans-cyclooctene and either thiol-maleimide (AgUox-MAL-HSA) or -APN chemistry (AgUox-APN-HSA). Substantial cleavage of the thioester of AgUox-MAL-HSA was observed in vitro, whereas no cleavage of the thiol-APN product of AgUox-APN-HSA was observed. Furthermore, the in vivo serum half-life of AgUox-APN-HSA in the late phase was significantly longer than that of AgUox-MAL-HSA. Overall, these results demonstrate that the thiol-APN chemistry enhanced the in vivo stability of the HSA-conjugated therapeutic protein.

Soluble expression of bioactive recombinant porcine-human chimeric uricase mutant employing MBP-SUMO fusion system

Urate oxidase is a promising biological medicine for hyperuricemia treatment, but immunogenicity obstructs the development of its clinical application. The recombinant porcine-human chimeric uricase mutant named dHU-wPU is a humanized chimeric uricase based on wild porcine uricase (wPU), which can effectively reduce the limitation of potential immunogenicity with a high homology (92.76%) to deduced human uricase (dHU). Unfortunately, the insoluble expression form of dHU-wPU in E. coli increases the difficulty of production. In this study, we described a more convenient method to efficiently obtain recombinant dHU-wPU protein from E. coli. Combination small ubiquitin-related modifier protein (SUMO) and maltose-binding protein (MBP) was employed to achieve the soluble expression of dHU-wPU. MBP-SUMO-dHU-wPU fusion protein was not only overexpressed in a soluble form, but also showed high purification and cleavage efficiency. Subsequently, we optimized the culture conditions of shake flasks and expanded the production of MBP-SUMO-dHU-wPU fusion protein in a 5 L bioreactor. Finally, about 15 mg of recombinant dHU-wPU was obtained from 1 L M9 fermentation culture by using two-step affinity chromatography, with a SDS-PAGE purity over 90%. In vitro activity analysis showed that dHU-wPU had better ability to catalyze uric acid than wPU.

Single-Dose Rasburicase Might Be Adequate To Overcome Tumor Lysis Syndrome In Hematological Malignancies

IntroductionTumor lysis syndrome (TLS) is a commonly observed oncological emergency that requires prompt diagnosis and treatment. Rasburicase is a recombinant urate oxidase endorsed in TLS for the treatment of hyperuricemia. The effect of single-dose 7.5 mg rasburicase at longer follow-ups was not widely investigated. Patients and MethodsEighty-two patients included in the study with clinical TLS and laboratory TLS. The primary endpoint was the normalization of uric acid (<6mg/dL) within 24 hours of rasburicase administration, which was described as treatment success. The secondary endpoint was defined as having sustained response at the first week. The third endpoint was defined as the reaching the baseline renal function before TLS. ResultsWe found that the use of a 7.5 mg dose of rasburicase controlled uric acid in 74 of 82 (90,2%) patients at the 24th hour. In the first week, uric acid remained at normal levels in 69 of 82 (84,1%) patients. At 24 hours, the TLS risk group was the only predictor for failing uric acid normalization; at the end of the first week, no predictive factor was identified for failing uric acid normalization. ConclusionRasburicase at 7.5 mg dose is an important agent for controlling laboratory and clinical TLS at 24 hours and extending its effect to the first week.

Thermostable and Long-Circulating Albumin-Conjugated Arthrobacter globiformis Urate Oxidase.

Urate oxidase derived from Aspergillus flavus has been investigated as a treatment for tumor lysis syndrome, hyperuricemia, and gout. However, its long-term use is limited owing to potential immunogenicity, low thermostability, and short circulation time in vivo. Recently, urate oxidase isolated from Arthrobacter globiformis (AgUox) has been reported to be thermostable and less immunogenic than the Aspergillus-derived urate oxidase. Conjugation of human serum albumin (HSA) to therapeutic proteins has become a promising strategy to prolong circulation time in vivo. To develop a thermostable and long-circulating urate oxidase, we investigated the site-specific conjugation of HSA to AgUox based on site-specific incorporation of a clickable non-natural amino acid (frTet) and an inverse electron demand Diels–Alder reaction. We selected 14 sites for frTet incorporation using the ROSETTA design, a computational stability prediction program, among which AgUox containing frTet at position 196 (Ag12) exhibited enzymatic activity and thermostability comparable to those of wild-type AgUox. Furthermore, Ag12 exhibited a high HSA conjugation yield without compromising the enzymatic activity, generating well-defined HSA-conjugated AgUox (Ag12-HSA). In mice, the serum half-life of Ag12-HSA was approximately 29 h, which was roughly 17-fold longer than that of wild-type AgUox. Altogether, this novel formulated AgUox may hold enhanced therapeutic efficacy for several diseases.

Structural and biochemical insights into a hyperthermostable urate oxidase from Thermobispora bispora for hyperuricemia and gout therapy

Microbial urate oxidase has emerged as a potential source of therapeutic properties for hyperuricemia in arthritic gout and renal disease. The thermostability and long-term thermal tolerance of the enzyme need to be established to prolong its therapeutic effects. Here, we present the biochemical and structural aspects of a hyperthermostable urate oxidase (TbUox) from the thermophilic microorganism Thermobispora bispora. Enzymatic characterization of TbUox revealed that it was active over a wide range of temperatures, from 30 to 70 °C, with optimal activity at 65 °C and pH 8.0, which suggests its applicability under physiological conditions. Moreover, TbUox exhibits high thermostability from 10 to 65 °C, with Tm of 70.3 °C and near-neutral pH stability from pH 7.0 to 8.0 and high thermal tolerance. The crystal structures of TbUox revealed a distinct feature of the C-terminal loop extensions that may help with protein stability via inter-subunit interactions. In addition, the high thermal tolerance of TbUox may be contributed by the extensive inter-subunit contacts via salt bridges, hydrogen bonds, and hydrophobic interactions. The findings in this study provide a molecular basis for the thermophilic TbUox urate oxidase for application in hyperuricemia and gout therapy.

The role of thrifty genes in the origin of alcoholism: A narrative review and hypothesis.

In this narrative review, we present the hypothesis that key mutations in two genes, occurring 15 and 10million years ago (MYA), were individually and then collectively adaptive for ancestral humans during periods of starvation, but are maladaptive in modern civilization (i.e., "thrifty genes"), with the consequence that these genes not only increase our risk today for obesity, but also for alcoholism. Both mutations occurred when ancestral apes were experiencing loss of fruit availability during periods of profound climate change or environmental upheaval. The silencing of uricase (urate oxidase) activity 15MYA enhanced survival by increasing the ability for fructose present in dwindling fruit to be stored as fat, a consequence of enhanced uric acid production during fructose metabolism that stimulated lipogenesis and blocked fatty acid oxidation. Likewise, a mutation in class IV alcohol dehydrogenase ~10MYA resulted in a remarkable 40-fold increase in the capacity to oxidize ethanol (EtOH), which allowed our ancestors to ingest fallen, fermenting fruit. In turn, the EtOH ingested could activate aldose reductase that stimulates the conversion of glucose to fructose, while uric acid produced during EtOH metabolism could further enhance fructose production and metabolism. By aiding survival, these mutations would have allowed our ancestors to generate more fat, primarily from fructose, to survive changing habitats due to the Middle Miocene disruption and also during the late-Miocene aridification of East Africa. Unfortunately, the enhanced ability to metabolize and utilize EtOH may now be acting to increase our risk for alcoholism, which may be yet another consequence of once-adaptive thrifty genes.

Metformin restores cisplatin cytotoxicity reduced by allantoin in CML in vitro

Tumor lysis syndrome (TLS) is a metabolic disorder that mainly affects patients with malignant hematological neoplasms, and its development is frequently related to uric acid accumulation (hyperuricemia). Rasburicase is a recombinant urate oxidase enzyme applied to treat and avoid TLS converting urate into allantoin, a compound easily eliminated by the kidneys. However, a recent study by the authors demonstrated <em>in vitro</em> that an elevated allantoin generation, which has been observed in oncological patients treated with rasburicase, reduced cisplatin cytotoxicity in a non‑small cell lung cancer cell line (H460). Thus, it is necessary to determine the effects of the concomitant use of cisplatin and rasburicase for the treatment of patients with chronic myeloid leukemia (CML); due to the higher incidence of tumor lysis syndrome among patients with CML, it is necessary to search for adjuvant agents that can restore cisplatin cytotoxicity. Among adjuvant agents, metformin is of interest as it is effective, safe and has established pharmacological parameters. Thus, the present study evaluated the capacity of metformin to restore allantoin‑reduced cisplatin cytotoxicity in a CML cell line (K562) <em>in vitro</em>. The cells were treated with metformin (0.1, 0.25, 0.5, 0.6025, 2, 2.5 and 3 mM), cisplatin (15, 16.5, 20, 30 and 33 <em>µ</em>M), allantoin (100 and 200 <em>µ</em>g/ml), or their combinations for 48 h. Cell viability, cell cycle, morphological analysis and nuclear magnetic resonance experiments were performed. The results revealed that allantoin reduced cisplatin cytotoxicity in the K562 cell line. Thus, metformin synergistically increased cisplatin‑induced cell death and restored the cisplatin cytotoxicity that was reduced by allantoin.

Enhancement of Thermostability of Aspergillus flavus Urate Oxidase by Immobilization on the Ni-Based Magnetic Metal-Organic Framework.

The improvement in the enzyme activity of Aspergillus flavus urate oxidase (Uox) was attained by immobilizing it on the surface of a Ni-based magnetic metal–organic framework (NimMOF) nanomaterial; physicochemical properties of NimMOF and its application as an enzyme stabilizing support were evaluated, which revealed a significant improvement in its stability upon immobilization on NimMOF (Uox@NimMOF). It was affirmed that while the free Uox enzyme lost almost all of its activity at ~40–45 °C, the immobilized Uox@NimMOF retained around 60% of its original activity, even retaining significant activity at 70 °C. The activation energy (Ea) of the enzyme was calculated to be ~58.81 kJ mol−1 after stabilization, which is approximately half of the naked Uox enzyme. Furthermore, the external spectroscopy showed that the MOF nanomaterials can be coated by hydrophobic areas of the Uox enzyme, and the immobilized enzyme was active over a broad range of pH and temperatures, which bodes well for the thermal and long-term stability of the immobilized Uox on NimMOF.

Rasburicase and Glucose 6-Phophaste Dehydrogenase: Clinical Utility in the Management of Acute Leukemia Related Hyperuricemia

Background: Rasburicase is a recombinant urate oxidase enzyme commonly used to treat hyperuricemia of malignancy especially in cases with associated renal failure and very high uric acid level. However, it is contraindicated in patients with glucose 6-phosphate dehydrogenase (G6PD) deficiency as it may lead to increased hemolysis and methemoglobinemia, and rarely anaphylactic reaction. G6PD level evaluation is indicated prior to rasburicase administration. Here we sought to analyze the incidence of toxicity, level of G6PD in association with rasburicase in patients with acute leukemia.Methods: The Mayo Clinic database was interrogated using terms, acute leukemia, rasburicase and G6PD. Patients with acute leukemia and documented G6PD result who received rasburicase were selected. Time interval from documented G6PD report and rasburicase administration; concomitant hemoglobin level, and white blood cell count and creatinine level was collected.Results: One hundred sixteen patients with G6PD level and/or rasburicase use were identified. Thirty eight (36%) patients (AML 27, ALL 2, MPN 3, and lymphoma 6) received rasburicase, and 33 of them have concomitant G6PD level. The median (range) age was 76 years (27-91), and male accounted for 79% (30/38). The median (range) hemoglobin (gm/dL), uric acid (gm/dL) and creatinine (gm/dL) level was 9.1 (5.6-14.7), 12 (8-27) and 1.8 (0.8-4) respectively. All patients were reported to be non-Hispanic White except one with Asian ancestry. The G6PD level was high, normal, and low in 15 (39%), 13 (34%), and 5 (13%) patients respectively. Rasburicase was given without G6PD level in 5 (13%) patients, before the result for G6PD level available in 6 (16%) patients, and 4 (11%) had low level of G6PD; and none of them develop documented side effects.Conclusion: G6PD level is very variable at the time of diagnosis of hemological malignancies, and checking its level before rasburicase may have very limited clinical utility in certain patient groups. DisclosuresNo relevant conflicts of interest to declare.

English

BACKGROUND Rasburicase (recombinant urate oxidase) has been proven to be an effective therapy for prevention of tumour lysis syndrome (TLS). The recommended daily dosing regimen of rasburicase is 0.2 mg/kg/day for 5 days which is expensive and unaffordable to many patients in the developing countries. The purpose of the present study was to evaluate the effect of single 1.5 mg dose rasburicase in the management of tumour lysis syndrome. METHODS This is a follow-up study done at our institute. Fifty (50) patients with tumour lysis syndrome who received rasburicase from August 2015 to January 2020 were enrolled in this study RESULTS Single dose of rasburicase is effective in decreasing serum uric acid level in significant number (N = 41) of patients. Percentage of patients having uric acid less than 7 mg after single dose of rasburicase in 48 hours - 82.9 % (N = 34) while 17 % (N = 7) were found to have uric acid levels of more than 7 mg/dl. The percentage of patients with uric acid levels more than 7 mg/dl reduced from 36.5 % after 24 hours to 17 % after 48 hours. This indicates that the uric acid levels show a declining trend even after 24 hours without giving an additional dose of rasburicase. There was no relationship between uric acid levels at 24 hours and percentage change in creatinine level from baseline to 24 hours (correlation coefficient (r) = -0.047, P = 0.770. Patients who required additional dose (N = 9) had high base line value of uric acid and their high value was maintained over the follow up period of three days. Patients with pre exiting kidney disease and high level of baseline uric acid also needed dialysis (N = 3). CONCLUSIONS In majority of patients, a single 1.5 mg dose of rasburicase is an effective way to reduce raised uric acid in appropriate circumstances. KEYWORDS Single Dose, Recombinant Urate Oxidase, Uric Acid, Leukemia, Tumour Lysis Syndrome, Rasburicase

“Resurrected” human-source urate oxidase with high uricolytic activity and stability

As evidences showed that UOX(Gene ID: 391051), a single pseudogene formed after multiple mutations during human evolution, could be transcribed to mature mRNA and translated to two short peptides, we hypothesized that urate oxidase with higher homology with deduced human urate oxidase (dHU) might have lower immunogenicity. In this work, we constructed a "resurrected" human-source urate oxidase (rHU19) based on dHU. It obtained better uricolytic activity (8.29 U/mg) and catalytic efficiency (3.32 s−1 μM−1) compared with wild porcine urate oxidase (wPU) and FDA-approved porcine–baboon chimera (PBC). Maintaining high homology with dHU (93.75 %), rHU19 could be more suitable for the treatment of gout and hyperuricemia theoretically.

Hepatic and Renal Impacts of Lesinurad on Experimental Hyperuricemia: Biochemical, Molecular and Pathological Investigations.

&lt;b&gt;Background and Objective:&lt;/b&gt; Hyperuricemia is one of the most dangerous threats to human life. It is mainly associated with gout and inflammatory arthritis. Therefore, finding a safe medication that does not have severe side-effects is a goal shared by most physicians. The current study aimed to evaluate the effect of lesinurad (Zurampic; ZUR) and allopurinol (ALP), both alone or in combination, on the treatment of hyperuricemic mice at the biochemical, molecular and cellular levels. &lt;b&gt;Materials and Methods:&lt;/b&gt; Lesinurad and allopurinol were orally administered to hyperuricemic and control mice for seven consecutive days, either alone or in combination. Levels of uric acid and xanthine oxidase activity, blood urea nitrogen, creatinine, ALT and AST were measured in the serum. The mRNA expression of mouse hepatic guanine deaminase (Gda), purine nucleotide phosphorylase (PNP), renal urate anion transporter-1 (URAT-1) and OAT-1 transporters were examined. The renal tissues were examined using H and E staining and the immunoreactivity technique. &lt;b&gt;Results:&lt;/b&gt; Lesinurad and allopurinol administration resulted in a significant decrease in serum levels of uric acid, blood urea nitrogen and xanthine oxidase activity reported in hyperuricemic mice. Both partially reversed oxonate-induced alterations in renal mURAT-1 and mOAT-1 expressions, as well as alterations in the immunoreactivity of Bcl2. All showed an increase in renal uric acid secretion and excretion. ALP and ZUT significantly decreased the increase in Gda and PNP expression reported in hyperuricemic mice. The combined administration of ZUR and ALP restored and improved renal function histopathological changes reported in hyperuricemic mice. &lt;b&gt;Conclusion:&lt;/b&gt; The hypouricemic impact of both lesinurad and allopurinol in the treatment of hyperuricemia in mice was confirmed following hyperuricemia treatment.

Molecular Elucidation of a Urate Oxidase from Deinococcus radiodurans for Hyperuricemia and Gout Therapy.

Urate oxidase initiates the uric acid degradation pathways and is extensively used for protein drug development for gout therapy and serum uric acid diagnosis. We first present the biochemical and structural elucidation of a urate oxidase from the extremophile microorganism Deinococcus radiodurans (DrUox). From enzyme characterization, DrUox showed optimal catalytic ability at 30 °C and pH 9.0 with high stability under physiological conditions. Only the Mg2+ ion moderately elevated its activity, which indicates the characteristic of the cofactor-free urate oxidase family. Of note, DrUox is thermostable in mesophilic conditions. It retains almost 100% activity when incubated at 25 °C and 37 °C for 24 h. In this study, we characterized a thermostable urate oxidase, DrUox with high catalytic efficiency and thermal stability, which strengthens its potential for medical applications.

Multivalent Albumin-Neonatal Fc Receptor Interactions Mediate a Prominent Extension of the Serum Half-Life of a Therapeutic Protein.

Human serum albumin (HSA) has been used to extend the serum half-life of therapeutic proteins owing to its exceptionally long serum half-life via the neonatal Fc receptor (FcRn)-mediated recycling mechanism. In most cases, only one HSA molecule was conjugated to a therapeutic protein, leading to a limited extension of the serum half-life. In this study, we hypothesized that conjugation of multiple HSA molecules to a therapeutic protein significantly further extends the serum half-life via multivalent HSA-FcRn interactions. We chose urate oxidase (Uox), a tetrameric therapeutic protein used for the treatment of gout, as a model. In previous studies, only one HSA molecule was site-specifically conjugated to one Uox because of poor conjugation yield of the relatively slow bio-orthogonal chemistry, strain-promoted azide-alkyne cycloaddition (SPAAC). To increase the number of HSA molecules conjugated to one Uox, we employed the faster bio-orthogonal chemistry, inverse electron demand Diels-Alder reaction (IEDDA). We site-specifically introduced the phenylalanine analog with a fast-reacting tetrazine group (frTet) into position 174 of each subunit of Uox. We then achieved site-specific HSA conjugation to each subunit of Uox via IEDDA, generating Uox conjugated to four HSA molecules (Uox-HSA4), with a small portion of Uox conjugated to three HSA molecules (Uox-HSA3). We characterized Uox-HSA4 as well as Uox variants conjugated to one or two HSA molecules prepared via SPAAC (Uox-HSA1 or Uox-HSA2). The enzyme activity of all three Uox-HSA conjugates was comparable to that of unmodified Uox. We found out that an increase in HSA molecules conjugated to Uox (multiple albumin-conjugated therapeutic protein) enhanced FcRn binding and consequently prolonged the serum half-life in vivo. In particular, the conjugation of four HSA molecules to Uox led to a prominent extension of the serum half-life (over 21 h), which is about 16-fold longer than that of Uox-WT.

Hyperuricemia causes kidney damage by promoting autophagy and NLRP3-mediated inflammation in rats with urate oxidase deficiency.

ABSTRACTEpidemiological research has shown that elevated serum urate concentration is a risk factor for the development of kidney disease; however, the mechanisms underlying this process have not yet been elucidated. To examine the role of urate in the kidney, we used Wistar rats to functionally disrupt expression of urate oxidase (UOX) by using the CRISPR/Cas9 system. In comparison to wild-type (WT) rats, serum urate levels spontaneously and persistently increased in UOX-KO rats, without showing a significant decrease in survival rate. Architecture and function of the kidneys in UOX-KO rats were impaired. Injury to the kidney resulted in increased interstitial fibrosis, macrophage infiltration, increased expression of NLRP3 and IL-1β, and activation of multiple cell-signaling pathways associated with autophagy, such as AMPK, p38 MAPK, ERK and JNK pathways. Inhibition of autophagy with the PI3K inhibitor 3-MA abrogated the development of kidney damage and attenuated renal fibrosis, macrophage infiltration, and expression of NLRP3 and IL-1β in injured kidneys. In conclusion, the UOX-KO rat is a great model to study hyperuricemia-related diseases. Hyperuricemia-induced autophagy and NLRP3-dependent inflammation are critically involved in the development of renal damage and, therefore, highlight the inhibition of autophagy and inflammation in search of therapeutic strategies to treat uric acid nephropathy.

Pharmacologic Targeting of BET Proteins Attenuates Hyperuricemic Nephropathy in Rats.

Hyperuricemia is an independent risk factor for renal damage and promotes the progression of chronic kidney disease. In this study, we investigated the effect of I-BET151, a small-molecule inhibitor targeting the bromodomain and extraterminal (BET) proteins, on the development of hyperuricemic nephropathy (HN), and the mechanisms involved. Expression levels of bromodomain-containing protein 2 and 4, but not 3 were increased in the kidney of rats with HN; administration of I-BET151 effectively prevented renal dysfunction, decreased urine microalbumin, and attenuated renal fibrosis as indicated by reduced activation of renal interstitial fibroblasts and expression of fibronectin and collagen I in HN rats. Mechanistic studies show that I-BET151 treatment inhibited transition of renal epithelial cells to a mesenchymal cell type as evidenced by preservation of E-cadherin and reduction of vimentin expression. This was coincident with reduced expression of TGF-β1 and dephosphorylation of Smad3 and ERK1/2. I-BET151 was also effective in inhibiting phosphorylation of NF-κB, expression of multiple cytokines and chemokines, and infiltration of macrophages to the injured kidney. Although there were increased serum levels of uric acid and xanthine oxidase, an enzyme that catalyzes production of uric acid, and decreased expression of renal organic anion transporter 1 and 3 that promote urate excretion in the model of HN, and reduced expression levels of urine uric acid, I-BET151 treatment did not affect these responses. Collectively, our results indicate that I-BET151 alleviates HN by inhibiting epithelial to mesenchymal transition and inflammation in association with blockade of TGF-β, ERK1/2 and NF-κB signaling.

Lactose inducible fermentation in Escherichia coli for improved production of recombinant urate oxidase: Optimization by statistical experimental designs

Abstract The enzyme urate oxidase (UOX) is used as a drug for preventing and treatment of hyperuricemia. This study deals with the statistical optimization of lactose inducible fermentation for production of soluble recombinant Aspergillus flavus UOX. 10 independent variables were investigated by Plackett–Burman design (PBD), and the most significant factors were further optimized by central composite design (CCD). PBD results indicated that glycerol, yeast extract, tryptone, and lactose affected UOX activity significantly. The CCD results showed that the maximum enzyme activity (19.34 U/ml) and biomass concentration (44.0 g/L) can be achieved under the optimum conditions of glycerol 0.87 g/L, yeast extract 9.11 g/L, tryptone 10.29 g/L, K2HPO4 1.81 g/L, and lactose 12.79 g/L. When the same induction strategy was tested at shake flask, 19.34 U/mL of UOX activity was obtained, which was 12.5 folds higher than IPTG induction protocol. Furthermore, the lower total cost (€0.7 vs. €13.5) was additional feature that confirmed the suitability of the lactose induction method. Collectively, our results showed that design of experiment methodology can be applied as a suitable tool for improved production of UOX enzyme using lactose as the inducer.

Heterologous expression of recombinant urate oxidase using the intein-mediated protein purification in Pichia pastoris.

The potential of urate oxidase (uricase) for clinical use has been highlighted because of its role in lowering the blood uric acid levels for the treatment of tumor lysis syndrome. In the present study, the codon-optimized synthetic gene of Aspergillus flavus uricase was fused to the Mxe GyrA intein and chitin-binding domain. The construct was inserted into pPICZA and pPICZαA vectors and electroporated into Pichia pastoris GS115 for the cytosolic and secretory expression. Transformants were screened on gradients of Zeocin up to 2000μg/ml to find multi-copy integrants. For both constructs, colonies with more resistance were screened for the highest uricase producers by enzyme assay. PCR analysis confirmed successful cassettes insertion into the genome and Mut + phenotype. The gene copy index was determined to be two and five for cytosolic and secretory strains, respectively. Productivity of the cytosolic and secretory strains was found to be 0.74 and 0.001 U/ml culture media in order while the cytosolic recombinant enzyme accounted for about 6% of total proteins. One-step purification of the expressed uricase was done with the aid of the chitin affinity column, followed by DTT induction for intein on-column cleavage. The yield of 40.8mg/L and K m of 0.22mM was obtained for intracellular expression. It seems that the intracellular production of uricase can indeed serve as an effective alternative to secretory expression. Moreover, this is the first report considering cytosolic production of uricase using the intein-mediated protein purification in the methylotrophic yeast, P. pastoris.

Process development of recombinant Aspergillus flavus urate oxidase production in Pichia pastoris intracellularly and its characterization as a potential biosimilar

Recombinant A. flavus Urate Oxidase (rUOX), which catalyzes uric acid to allantoin, is highly effective in treating tumor lysis syndrome (TLS). However, its production process is quite complicated, and its use as a therapy is often prohibitive because of the high cost. In this work, we demonstrate, for the first time, a new bioprocess for the production of rUOX expressed in P. pastoris GS115 intracellularly in a soluble and active form, which aims to develop biosimilars that address the current limitations. For the downstream process, the homogenate clarification and intermediate purification were rationally designed with regards to protein characteristics, including polyethyleneimine precipitation, ammonium sulfate precipitation, and flow-through module anion-exchange chromatography. Response surface methodology (RSM) was conducted to optimize the cation exchanger polishing step to determine the appropriate conditions that satisfy the purity and yield requirements. Finally, 2.2 g rUOX (99% purity) was obtained from the 1 l fermentation broth. Various characterizations were carried out to confirm rUOX’s similarity to its commercial counterpart with regards to both physicochemical and enzymatic aspects. Overall, the rUOX derived from P. pastoris has the potential to be used in therapeutic applications.

The Effective Control of Hyperuricemia in Cancer Patients: A New Recombinant Conjugated Variant of Urate Oxidase.

Objective: Management of hyperuricemia is crucial to controlling tumor lysis syndrome (TLS) during cancer therapy. Urate oxidase (UOX) that catalyzes the enzymatic oxidation of uric acid into allantoin, is effective in lowering plasma uric acid levels and controlling hyperuricemia. Recently, we developed a new recombinant conjugate variant of UOX therapeutic drug using PASylation technology. This study was designed to evaluate the stability, plasma half-life and immunogencity of PASylated UOX. Methods:A recombinant variant of PASylated UOX from the Aspergillus flavus was manufactured using bioinformatics and experimental techniques. Ex vivo evaluation of stability of PASylated UOX was done in 50% human serum. For half-life test, recombinant PASylated UOX and rasburicase were administered at 1.5 mg/kg to 10 rats in two different groups and samples were collected after injection Production of antibodies against PASylated drug was also assayed. Results:Residual activity of PASylated UOX in 50% human serum was higher than rasburicase and native UOX. Stability of PASylated UOX at 25°C and 37°C was also higher than rasburicase and native UOX. The PASylated half-life was ~32.1 hours, whereas half-life for rasburicase and native UOX was ~25.1 and ~22.8 hours, respectively. In immunogenicity examination, there is 33% and 36% decrease in the absorbance of native UOX and rasburicase, respectively when compared with that of PASylated UOX.Conclusion:Our data confirmed the efficacy and stability of PASylated UOX in comparison to the rasburicase. In summary, the results indicated that PASylated UOX drug is effective at lowering plasma uric acid levels with prolonged plasma half-life and decreased cost.