Screening and characterization of new enzymes for biosensing and analytics

The development of new or improved analytical methods requires new enzymes. Screening techniques utilizing enrichment cultures and rapid assay methods supported by automated or miniaturized methods are useful tools to detect new enzyme producers. Notably, oxidoreductases are well suited for analytical purposes. The NAD(P)- and oxygen-independent quinoprotein dehydrogenases with a covalently bound redox cofactor can be used advantageously for the development of biosensors. Examples are given of selective enrichment methods used in screening for useful enzyme-producing microorganisms. Enrichment under chemostatic conditions proved to be successful because enzymes with a remarkably high affinity against the analyte could be obtained. This is demonstrated by the screening of a trimethylamine-converting enzyme. The frequently observed high selectivity of these enzymes against the substrate is demonstrated in a few examples. In exploitation of these new oxidoreductases, new analytical methods were developed which are useful for the detection and during monitoring of phenylketonuria (PKU) or maple syrup urine disease (MSUD).