SEMICARBAZIDE-SENSITIVE AMINE OXIDASES IN SHEEP PLASMA - INTERACTIONSWITH SOME SUBSTRATES AND INHIBITORS

The present study has examined the affinities of sheep plasma semicarb azide-sensitive amine oxidase (SSAO) enzymes for a range of aliphatic amines and also the effects of two inhibitory compounds, beta-aminopro pionitrile (BAPN) and mexiletine. Two kinetically separable enzyme act ivities appeared to be responsible for the metabolism of amines contai ning 2-5 carbon atoms while the deamination of higher amines and methy lamine and allylamine produced kinetic plots characteristic of only on e enzyme activity. When benzylamine metabolism was used as an indicati on of enzyme activity, the two inhibitors had different effects. BAPN exhibited predominantly a mixed pattern of inhibition while the effect s of low concentrations of mexiletine were largely competitive. These results present evidence confirming the presence of two kinetically se parable SSAO activities in sheep plasma, although we must await the de velopment of highly selective inhibitors before these two activities c an be fully resolved.