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

Plasmid expression of Deinococcus radiodurans RecA confers UV-A protection to Escherichia coli with an inverse protein dose dependence, which does not exceed conspecific RecA protection

Low level expression in Escherichia coli of the RecA protein from the radiation resistant bacterium Deinococcus radiodurans protects a RecA deficient strain of E. coli from UV-A irradiation by up to ∼160% over basal UV-A resistance. The protection effect is inverse protein dose dependent: increasing the expression level of the D. radiodurans RecA (DrRecA) protein decreases the protection factor. This inverse protein dose dependence effect helps resolve previously conflicting reports of whether DrRecA expression is protective or toxic for E. coli. In contrast to the D. radiodurans protein effect, conspecific plasmid expression of E. coli RecA protein in RecA deficient E. coli is consistently protective over several protein expression levels, as well as consistently more protective to higher levels of UV-A exposure than that provided by the D. radiodurans protein. The results indicate that plasmid expression of D. radiodurans RecA can modestly enhance the UV resistance of living E. coli, but that the heterospecific protein shifts from protective to toxic as expression is increased.

Cloning, Heterologous Expression, and Characterization of a Neutral Uricase from Arthrobacter sp. CSAJ-16 in Cangshan Mountain

Uricase (or Urate oxidase), a key enzyme involved in purine metabolism, is commonly used in treating conditions such as gout, hyperuricemia, and tumor lysis syndrome. In this study, a uricase-producing strain (named CSAJ-16) was isolated from the soil sample of Cangshan Mountain, Yunnan Province, China. This strain was identified as Arthrobacter sp. CSAJ-16. Based on the gene sequence alignment, the uricase gene (named aruox) of Arthrobacter sp. CSAJ-16 was amplified and heterologously expressed. The recombinant uricase (ArUOX) was about 32 kDa. The optimal pH and temperature of ArUOX were pH 7 and 20°C, respectively. The ArUOX remained above 50% relative activity after incubation at 37°C for 100 min or at pH 6.0-8.6 for 24 h. Moreover, metal ions such as K+, Mg2+, Ca2+, Ba2+ and Pb2+ can significantly enhance the activity of ArUOX (> 200%). These enzymatic properties indicate that ArUOX has potential applications in pharmaceutical enzymes and uric acid detection kits.

Rational design of mini protein mimicking uricase: Encapsulation in ZIF-8 for uric acid detection

Five mini proteins mimicking uricase comprising 20, 40, 60, 80, and 100 amino acids were designed based on the conserved active site residues within the same dimer, using the crystal structure of tetrameric uricase from Arthrobacter globiformis (PDB ID: 2yzb) as a template. Based on molecular docking analysis, the smallest mini protein, mp20, shared similar residues to that of native uricase that formed hydrogen bonds with uric acid and was chosen for further studies. Although purified recombinant mp20 did not exhibit uricase activity, it showed specific binding towards uric acid and evinced excellent thermotolerance and structural stability at temperatures ranging from 10°C to 100°C, emulating its natural origin. To explore the potential of mp20 as a bioreceptor in uric acid sensing, mp20 was encapsulated within zeolitic imidazolate framework-8 (mp20@ZIF-8) followed by the modification on rGO-screen printed electrode (rGO/SPCE) to maintain the structural stability. An irreversible anodic peak and increased semicircular arcs of the Nyquist plot with an increase of the analyte concentrations were observed by utilizing cyclic voltammetry and electrochemical impedance spectroscopy (EIS), suggesting the detection of uric acid occurred, which is based on substrate-mp20 interaction.

Enzymes and Enzyme Inhibitors—Applications in Medicine and Diagnosis

This is the first part of a Special Issue on enzymes and enzymes inhibitors and their applications in medicine and diagnosis [...]

Characterization of a novel marine microbial uricase from Priestia flexa and evaluation of the effects of CMCS conjugation on its enzymatic properties

A novel uricase producing marine bacterium Priestia flexa alkaAU was isolated and identified. The 16S rDNA and the uricase coding gene were sequenced, analyzed and submitted to GenBank. The uricase from Priestia flexa alkaAU (PFU) was purified, determined to be 58.87 kDa, and conjugated with carboxymethyl chitosan (CMCS) by ionic gelation. CMCS conjugation had no effect on the optimum pH of PFU but decreased the optimum temperature by 10 °C. CMCS conjugation increased the specific activity of PFU by 53% at the human body temperature (37 °C) and small intestine's pH (pH 6.8). Uricase thermostabilizing ability of CMCS was significant in the range of 37-80 °C but not at lower temperatures. For improvement of the pH stability of PFU, CMCS was more effective at pHs 3-5 than pHs 6-11. CMCS increased the half-life of PFU against artificial intestinal fluid by 1.5 folds, which demonstrated the potential capability of CMCS-PFU for oral administration.

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.