THE ROLE OF PEROXIDASE IN THE OLIGOMERIZATION OF 5-HYDROXYTRYPTAMINE INVESTIGATED BY MATRIX-ASSISTED-LASER-DESORPTION IONIZATION MASS-SPECTROMETRY/

The role of peroxidase in the melanogenesis of 5-hydroxytryptamine was investigated by matrix-assisted laser desorption/ionization mass spec trometry. in order to establish the role of hydrogen peroxide in the r eaction mixture, incubations were performed with peroxidase in the pre sence or absence of hydrogen peroxide, Samples were drawn from the rea ction environment at various times, ultrafiltered to remove the enzyme and immediately lyophilized, The results indicated that peroxidase pr omotes oligomerization of 5-hydroxytryptamine with the formation of di mers, trimers and tetramers, with kinetics which are faster than, but which have lower yields than, those achieved by tyrosinase, The presen ce of hydrogen peroxide in the peroxidase-5-hydroxytryptamine reaction mixture favours further oligomerization, leading to decamers, The rea ction of hydrogen peroxide with 5-hydroxytryptamine leads to results s imilar to those obtained in the presence of peroxidase plus hydrogen p eroxide, Therefore, the further oligomerization of 5-hydroxytryptamine by peroxidase requires the presence of hydrogen peroxide, whereas tyr osinase alone promotes a higher degree of 5-hydroxytryptamine oligomer ization. (C) 1998 John Wiley & Sons, Ltd.