Aerobic and Anaerobic Metabolism of Trimethylamine, Dimethylamine and Methylamine in Hyphomicrobium X

Abstract

Hyphomicrobium strain x was grown on trimethylamine and dimethylamine as the sole sources of carbon and energy under both aerobic and anaerobic conditions and the enzymes involved in the metabolism of these compounds were investigated. During aerobic growth of the organism on trimethylamine, accumulation and subsequent utilization of dimethylamine was observed. When the organism was grown on trimethylamine under anaerobic conditions in the presence of nitrate, a sequential accumulation and utilization of dimethylamine and methylamine was found. In cell-free extracts of Hyphomicrobium x grown on trimethylamine or dimethylamine under both aerobic and anaerobic conditions the following enzyme activities were detected: trimethylamine dehydrogenase, dimethylamine dehydrogenase, γ-glutamylmethylamide synthetase, N-methylglutamate dehydrogenase, methanol dehydrogenase, formaldehyde dehydrogenase, formate dehydrogenase and hydroxypyruvate reductase. Under neither growth condition were any of the following enzyme activities detected: trimethylamine mono-oxygenase, dimethylamine mono-oxygenase, trimethylamine-N-oxide aldolase (demethylase) and primary-amine dehydrogenase. Trimethylamine dehydrogenase and dimethylamine dehydrogenase were partially purified from bacteria grown on dimethylamine and the results suggest that in Hyphomicrobium x a novel enzyme, namely dimethylamine dehydrogenase, participates in the oxidation of dimethylamine.