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 spectrometry. in order to establish the role of hydrogen peroxide in the reaction mixture, incubations were performed with peroxidase in the presence or absence of hydrogen peroxide, Samples were drawn from the reaction environment at various times, ultrafiltered to remove the enzyme and immediately lyophilized, The results indicated that peroxidase promotes oligomerization of 5-hydroxytryptamine with the formation of dimers, trimers and tetramers, with kinetics which are faster than, but which have lower yields than, those achieved by tyrosinase, The presence of hydrogen peroxide in the peroxidase-5-hydroxytryptamine reaction mixture favours further oligomerization, leading to decamers, The reaction of hydrogen peroxide with 5-hydroxytryptamine leads to results similar to those obtained in the presence of peroxidase plus hydrogen peroxide, Therefore, the further oligomerization of 5-hydroxytryptamine by peroxidase requires the presence of hydrogen peroxide, whereas tyrosinase alone promotes a higher degree of 5-hydroxytryptamine oligomerization. (C) 1998 John Wiley & Sons, Ltd.