title: Multi-enzyme membrane electrodes for determination of creatinine and creatine in serum.
abstract: An enzyme electrode system for the determination of creatinine and creatine was developed by utilizing three enzymes: creatinine amidohydrolase (CA), creatine amidinohydrolase (Cl), and sarcosine oxidase (SO). These enzymes were co-immobilized onto the porous side of a cellulose acetate membrane with asymmetric structure, which has selective permeability to hydrogen peroxide. Two kinds of multi-enzyme electrodes were constructed by combining a polarographic electrode for sensing hydrogen peroxide and an immobilized CA/Cl/SO membrane or Cl/SO membrane for creatinine plus creatine or creatine, respectively. The multi-enzyme electrodes responded linearly up to 100 mg of creatinine and creatine per liter in human serum. Response time was 20 s in the rate method and the detection limit was 1 mg/L. Only 25 microL of serum sample is required. Analytical recoveries, precisions, and correlations with the Jaffé method were excellent, and the multi-enzyme electrodes were sufficiently stable to perform more than 500 assays. No loss of activity of immobilized enzymes was observed after nine months of storage at 4 degrees C in air.
mesh_terms: D000581:Amidohydrolases; D003401:Creatine / Q000097:blood*; D003404:Creatinine / Q000097:blood*; D004566:Electrodes; D004800:Enzymes, Immobilized; D006801:Humans; D006861:Hydrogen Peroxide / Q000032:analysis; D008567:Membranes, Artificial; D008722:Methods; D010089:Oxidoreductases, N-Demethylating; D050879:Sarcosine Oxidase; D014512:Ureohydrolases
chemical_list: D004800:Enzymes, Immobilized; D008567:Membranes, Artificial; D003404:Creatinine; D006861:Hydrogen Peroxide; D010089:Oxidoreductases, N-Demethylating; C494349:PIPOX protein, human; D050879:Sarcosine Oxidase; D000581:Amidohydrolases; D014512:Ureohydrolases; C019944:creatinase; D003401:Creatine