Disintergration of DNA molecules in human body results inUric acid, a natural product of metabolism, which is routinely expelled fromthe body.
On the other hand, high accretion of uric acid in the body and or lowelimination rate of it is firmly linked to pathogenesis of uman diseases suchas gout and hyperuricemia. It is extremely affected through the highconsumption of food rich in purine. Hyperuricemia results from animbalance between the rates of production and excretion of uric acid. Due tothe low solubility (6 mg/dL, 20 C) of uric acid, long-term hyperuricemia leadsto destructive crystalline urate deposits around joints, in soft tissues, andin some organs, causing a number of disorders, including gout and uratenephropathy associated with tumor lysis syndrome.
Studies have also shown thathyperuricemia in humans can increase the risk of cardiovascular diseases,chronic nephropathy, impaired renal function, hypertension, and stroke. Due tothose severe complications of hyperuricemia, its therapeutic countermeasureshave attracted great attention in the medical community. This disease afflictsmore than 10 million patients worldwide, and its incidence is on the rise. Morethan three decades ago allopurinol was considered as a first line drug whichregulate uric acid synthesis by inhibiting xanthine oxidase (XO) enzyme. Inaddition to allopurinol, febuxostat is also used to reduce the synthesis ofuric acid by inhibiting the XO enzyme and is approved by the European Medical Agencyin 2008 and US FDA in 2009. In contrast to allopurinol it acts on both reducedas well as oxidised form of XO. Partial relief from inflammation can beobtained by administration of hydroxychloroquine and non steroidal anti -inflammatory drugs. However these drugsare prone to have enormous side effects, so in order to regulate the uric acidlevel in serum or soft tissues, enzymatic treatment is considered to be thebetter way without any side effects.
Uricase (urate oxidase) EC 184.108.40.206 atetramer therapeutic enzyme which oxidatively opens the purine ring of uricacid and forms allantoin, CO2 and H2O. Allantoin is a soluble molecule inplasma, which can be easily eliminated through the kidneys as it is 5–10 timesmore soluble than uric acid.
Uricase enzyme is highly conserved present inmammals, plants, fungi, bacteria and yeasts but is absent in humans due toevolutionary mutations in uricase gene. Therefore,uricase from various microorganisms has been intravenously administered fornearly 40 years to treat hyperuricemia and gout. Rasburicase(Fasturtec®), a recombinant form of Uox from Aspergillus flavus, is the firstmarketed Uox preparation for the treatment and prophylaxis of acutehyperuricemia resulting from tumor lysis syndrome in children with cancer. Itsoutstanding ability to decrease uric acid level and dissolve tophi makesUox-based therapy a more promising strategy for the treatment of hyperuricemia.However, the clinical use of rasburicase is limited by its immunogenicity andshort half-life. In 2010, pegloticase (Krystexxa), a PEGylated chimericporcine-baboon Uox, was approved by the USA Food and Drug Administration (FDA)for treatment of chronic gout in adult patients refractory to conventionaltherapy. With a higher sequence homology to hypothetic human uricase and PEGylation,the immunogenicity of pegloticase is significantly reduced and half-lifeprolonged. In addition to the FDA approved porcine–baboon chimera (PBC),investigations on several other chimeric uricases have also been reported, suchas canine–human chimeric uricase and porcine–human chimeric uricase.
Thedevelopment of therapeutic uricase for human use is an intractable challenge asactivity, stability, and immunoreactivity should all be taken intoconsideration. As such, the medical community has a strong interest indeveloping a recombinant “human-like” uricase to treat hyperuricemia and gout.Uricase is localized inside microorganisms, especially Bacillus pasteurii,Proteus mirabilis, and Escherichia coli, while other microorganisms couldproduce them extracellularly by changing certain components of the culturemedia as in Streptomyces albosriseolus, Microbacterium, Bacillusthermocatenulatus, Candida tropicalis, and Pseudomonas aeruginosa. Streptomyces exofolitus isolated from soil by Magdaet al were found to be high producer of uricase. Uricase is a therapeutic enzyme belonging tothe class of the oxidoreductases, which catalyses the oxidation of uric acid,producing allantoin and acting in the purine degradation pathway.
The enzyme exists as a tetramer of identical subunits, each containing apossible type 2 copper-binding site. Urate oxidase is a homotetrameric enzyme containing four identical active sites situated at theinterfaces between its four subunits. It is unique among the oxidases in that it does not require a metal atom or an organic co-factorfor catalysis.Uric acid + O2 + H2O ? H2O2 + allantoin + CO2Uricase is useful for enzymaticdetermination of uric acid in biological fluids for clinical analysis. Uricasecan be also used as a protein drug to reduce toxic urate accumulation.
Immobilizeduricase can be used as a uric acid biosensor. Uricase is also used as anadditive in commercial formulations of hair coloring agents. Although uricasehas been produced using several microbial sources, due to its increasingimportance in treatment and in diagnosis, new sources of uricase are soughtaiming to produce better yield of the enzyme. The largest and most importantgenus in the order actinomycetales are Streptomyces.
It comprises up to90% of actinomycetes isolated from the soil samples, it is prolific producersof bioactive compounds such as antibiotics and enzymes which have importantapplications both in medicine and agriculture. The present study aimid at searching for potential uricase producing streptomycessource and cloning and expression and purification it.