Uricase function

A functional uricase was obtained by expression in E. coli of a soybean N-35 cDNA driven by the bacterial lacZ promoter (Suzuki Verma, 1991). The uricase activity was mainly found in the cytoplasmic fraction of E. coli and had the same pH optimum and apparent Km values as in the nodules. That N-35 is able to assemble into a functional, tetrameric holoenzyme in E. coli indicates that post-translational modifications, or the presence of peroxisomes, is not essential for its proper assembly and function in this organism. However, N-35 is not active and does not accumulate to any significant levels when it is expressed in transgenic tobacco under the control of the CaMV-35S promoter (our unpublished data). 

Suzuki, H. Verma, D.P.S. (1991). Soybean nodule-specific uricase (nodulin-35) is expressed and assembled into functional tetrameric holoenzyme in Escherichia coli. Plant Physiology 95, 384-9. 

Figure 6.5. Compatibility of organic osmolytes with enzyme function. (Upper panel) Pyruvate kinase of the marine crab Pachygrapsus crassipes. The effects of KC1 and NaCI and several organic solutes on the Km of phosphoenol pyruvate (PEP) (modified after Bowlus and Somero, 1979). (Middle panel) Malate dehydrogenase of the mangrove (Rhizophora mangle). Effects of NaCI and three organic osmolytes (the amino acid proline and the polyols pinitol and OMMI) on catalytic activity (modified after Sommer et al., 1990). (Bottom panel) Effects of NaCI and four osmolytes found in mammalian kidney (urea, glycine betaine, sorbitol, and inositol) on the Km of uric acid of uricase (modified after Yancey, 1992). (Figure modified after Somero and Yancey, 1997.)...

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