Simultaneous determination of enzyme activities by FTIR-spectroscopy in anone-step assay

The simultaneous quantification of beta-fructofuranosidase (invertase, EC 3 .2.1.26) and glucan 1,4-alpha-glucosidase amyloglucosidase, EC 3.2.1.3) act ivities in an one-step assay is reported. The approach is based on chemomet ric evaluation of the mid-IR spectra of the reaction mixture, measured with a sequential injection (SI) system with FTIR spectroscopic detection. Two partial least squares (PLS) calibration models were established automatical ly. The first model was calculated from reaction mixtures after the action of standard mixtures of both enzymes. The other was built up with mixtures of the substrates (maltose, sucrose) and products (fructose, glucose) witho ut any enzymatic reaction. The establishment of the second model was more r apid as no time for an enzymatic reaction is necessary. Both models gave co mparable results for the prediction of mixtures containing 0-2.0 U/ml of ea ch enzyme, with mean errors between 0.08 and 0.05 U/ml. (C) 1999 Elsevier S cience B.V. All rights reserved.