Abstract
Nitroblue tetrazolium (NBT)-glycinate assay was proposed as a suitable method of identification as well as determination for PQQ and quinoproteins by Fluckiger et al.[Biochem.Biophys.Res.Commun.153, 353(1988)] and Paz et al.[Biochem.Biophys.Res.Commun.154, 1330(1988)]. Before trying to applicate this assay method to our choline dehydrogenase preparation from rat liver, we investigated specificity of this assay method. It was ascertained that PQQ was the most reactive compound among investigated (minimum sensitivity : 1 pmol). Some coenzymes and some quinone compounds were also positive to the method although they were less sensitive. Some enzymes were also positive to it but with no correlation with the amount of enzyme. As a result, low specificity of the method will elicit erroneous results if one would insure the existence of quinone compound in his preparation by only this criterion. Our choline dehydrogenase preparation did not show proper redox-cycling in the method indicating the absence of quinoid compound in it.
