INVOLVEMENT OF METHYLTRANSFERASES ENZYMES DURING THE ENERGY METABOLISM OF THE ANAEROBIC ARCHAEON METHANOSARCINA SEMESIAE SP. NOV.

Abstract

The methyl group transfer from dimethylsulfide (DMS), trimethylamine and methanol to 2-mercaptoethanesulfonic acid (coenzyme M) were investigated from cell extracts of Methanosarcinasemesiae sp. nov. to evaluate whether the enzyme systems involved were constitutive or inductive.The extracts from cells grown on DMS exhibited methanogenic activity exclusively with DMS andmethanethiol. Likewise when cells were pre-grown on trimethylamine or methanol the extractsonly produced methane from the respective metaboilic substrate. Dimethylsulfide:methyl-coenzymeM transferase activity was dependent on ATP, but hydrogen did not stimulate activity. The factthat ATP could be replaced by the reductant Ti(III)-citrate indicates that reductive activation ofmethyl transfer reaction in DMS conversion proceeds in a manner similar to methyltransferasesinvolved in methanol and trimethylamine conversion, but with a different reduction source. Thissource appears to be limited since sometimes the cell extracts were totally inactive in the presenceof ATP, while still being activated with Ti(III)-citrate. It was concluded that enzymes involved inmethyl transfer reactions are specific for each substrate; DMS, trimethylamine and methanol andhave to be induced. Further investigations are recommended to corroborate the current study.