Lactate determination using substrate recycling

Amplification of the sensitivity of substrate or co-en me recycling is especially efficient in thermometric analysis since all the reactions involved frequently contribute to increasing the overall temperature change. One case in point is the determination of lactate or pyruvate by substrate recycling using co-immobilized lactate oxidase and lactate dehydrogenase [160]. 

The use of alkaline phosphatase as an enzyme label allows enhancement of the sensitivity by using phosphoenolpyruvate as substrate and the utilization of a separate detection column in the ET unit for the determination of the product (pyruvate) by substrate recycling. This is accomplished by using the substrate recycling system described above [18] comprising the coimmobilized enzymes lactate dehydrogenase (reduces pyruvate to lactate under the consumption of... 

Kiba N, Tomiyasu T and Furusawa M 1984 Flow enthalpimetric determination of glucose based on oxidation of 1,4-benzoquinone with use of immobilized glucose oxidase column Talanta 31 131-2 Scheller F, Siegbahn N, Danielsson B and Mosbach K 1985 High-sensitivity enzyme thermistor assay of L-lactate by substrate recycling Anal. Chem. 57 1740-3... 

In a sensor for lactate a bienzyme system composed of cytochrome 62 for lactate oxidation to pyruvate, and lactate dehydrogenase for conversion of pyruvate back to lactate has been used [321]. Hexacyanoferrate(III) served as electron acceptor for cytochrome b2- The reduced mediator was reoxidized at the electrode, thus giving a measuring signal depending on the analyte concentration. Attempts to determine both substrates of the recycling system have shown that, at tenfold amplification for lactate, the sensitivities for lactate and pyruvate are almost identical. The same recycling scheme has also been used in connection with Fe-EDTA as electron mediator in place of hexacyanoferrate(III) [336]. 

---