Determination of fructosyl amino acids and fructosyl peptides in protease-digested blood sample by a flow-injection system with an enzyme reactor.

A flow-injection system with an enzyme reactor was proposed for the measurement of fructosyl amino acids and fructosyl peptides in protease-digested blood samples. A fructosyl-amino acid oxidase (FAOX-TE) and two fructosyl-peptide oxidases (FPOX-CE and FPOX-CET) were covalently immobilized onto an inert support. They were used as the enzyme reactor in a FIA system with a hydrogen peroxide electrode. In particular, the FPOX-CET reactor possessed high selectivity for the detection of fructosyl valine (FV) and fructosyl valyl histidine (FVH) and an excellent operational stability. The proposed FIA system with the FPOX-CET reactor responded linearly to the concentration of FV over the dynamic range of 7.8 x 10(-6) to 5.8 x 10(-4) M. The present method could be successfully applied to the assay of FV and FVH in the protease-digested blood samples.