Transamidating enzymes. II. A continuous fluorescent method suited for automating measurements of factor XIII in plasma

The covalent incorporation of monodansylcadaverine (N-5-(aminopentyl)-5-dimethylamino-1-naphthalenesulfonamide) into some proteins, catalyzed by a variety of transamidases, is accompanied by marked changes in the fluorescence emission of the dansyl group. In addition to a blue shift, there is an increase in intensity of fluorescence. Various types of caseins, as well as succinylated β-lactoglobulin or lysozyme, can be used as protein acceptors, though neither of the latter two support the reaction in their native form. The continuous rise of fluorescence intensity made it possible to record directly the course of the enzymic transamidating reactions. As such, the procedure is well suited for automation. Furthermore, the assay is applicable to human plasma for the monitoring of fibrin-stabilizing factor (Factor XIII) levels.