Phenylketonuria in Turkey: experience with an enzymatic colorimetric test for measurement of serum phenylalanine

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).

A synopsis of the unconjugated acidic transamination metabolites of phenylalanine in phenylketonuria

We present blood and urine levels of unconjugated o-hydroxyphenylacetic, phenyllactic and phenylpyruvic acids in 61 children (2 years of age and above) and juveniles with phenylketonuria on or partially off diet. The samples were obtained during 185 scheduled outpatient visits and have been analysed with gas chromatographic methods. The compiled data define reference ranges of phenylalanine transamination capacity and of renal transport of metabolites which may be of value in further studies on the pathogenesis of phenylketonuria.