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find Author "PUJing" 1 results
  • Preparation and Identification of Recombinant Sarcosine Oxidase

    An important index determination for clinical diagnosis of renal function is to assay the creatinine concentration in serum. In the analytical process applied with coupled-enzyme, the quality control of sarcosine oxidase (SOX) as a key enzyme is the first problem to be solved. In order to establish an efficient and laboratory-scale production of SOX, the recombinant sarcosine oxidase (r-SOX) gene was a high-level expression in E.coli induced with lactose on a large-scale fermentation in 300 L fermenter. The results suggested that the biomass concentration reached OD600 of 22 and the expression of recombinant sarcosine oxidase in E. coli accounted for about 25% of total soluble protein in culture after fermentation. The cell-free extract obtained from high pressure homogenizer was processed by selective thermal denaturation and then purified with Ni-Sepharose FF chromatography. The sarcosine oxidase with 97% purity, 25 U/mg specific activity and 92.4% activity recovery was obtained. The molecular weight with single peptide chain of 53 kD and 55 kD of recombinant sarcosine oxidase was assessed by SDS-PAGE in presence or absence of 2-mercaptoehanol and Sephacryl S-200 chromatography. This sarcosine oxidase was found to be a conjugated protein, yellow enzyme, which combined with FAD as prosthetic group by covalent linkage. The contaminant of catalase was not detected in the sample pool of this enzyme. In addition, a further test to the thermal stability of sarcosine oxidase was done. According to the above results, the development and utilization of this enzyme has been set up on a reliable foundation.

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