Immobilized enzyme system for determination of sialic acid in serum or urine.
An immobilized enzyme system has been developed and employed to determine the concentration of sialic acid (N-acetylneuraminic acid) in human serum and urine. Two enzyme pairs, neuramindiase-Neu-5-Ac lyase and pyruvate oxidase-peroxidase, have been respectively co-immobilized onto 1,12-aminododecane-agarose with glutaraldehyde. The relative specific activity of the co-immobilized neuraminidase and Neu-5-Ac lyase were 60% and 78%, and those of pyruvate oxidase and peroxidase were 50% and 95% of the corresponding soluble enzymes, respectively. The optimal reaction pH at 37 degrees C for each of the co-immobilized enzymes was about one pH unit higher than that of the corresponding soluble enzyme. The optimal reaction temperature of each enzyme was increased as a result of immobilization. The thermal stability at 45 degrees C of the immobilized neuraminidase, Neu-5-Ac lyase, pyruvate oxidase, and peroxidase were increased 80-, 83-, 115-, and 147-fold, respectively. Km and Vm of each immobilized and co-immobilized enzyme have also been determined. The system provided a convenient and rapid method to determine the concentration of total sialic acid without pretreatment of the sample. The results correlated satisfactorily with those obtained by using a soluble enzyme system. The co-immobilized enzymes were stable for at least 1 year of 500 tests when used repeatedly. The system is thus a reproducible and reliable novel assay method for sialic acid in the serum or urine sample.
Department of Biochemistry, National Yang-Ming Medical College, Taipei, Taiwan, ROC.
C H
CH
Chien
Y H
YH
Wei
J F
JF
Shaw
D004800:Enzymes, Immobilized / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000378:metabolism*; D007652:Oxo-Acid-Lyases / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D011771:Pyruvate Oxidase / Q000378:metabolism*; D012794:Sialic Acids / Q000097:blood* / Q000652:urine
D004800:Enzymes, Immobilized; D012794:Sialic Acids; D010544:Peroxidases; D011771:Pyruvate Oxidase; D009439:Neuraminidase; D007652:Oxo-Acid-Lyases; C018728:N-acetylneuraminate lyase; D019158:N-Acetylneuraminic Acid