Competition between dopamine, beta-receptor agonists and promethazine in Escherichia coli plasmid replication.

The substrates in the phenylalanine, metabolism play key roles in the physiological processes of bacteria. Promethazine affects the phenylalanine metabolism in Escherichia coli. The antibacterial and anti-plasmid actions of promethazine were prevented by phenylalanine, tyrosine, phenylpyruvic acid, phenylacetic acid, noradrenaline and dopamine in minimal medium. Isoproterenol (and phenoxybenzamine) reduced, while propranolol, oxyprenolol and alprenolol isomers enhanced the anti-plasmid effect of promethazine. Propranolol itself induced an anti-plasmid effect. The effects of beta-receptor agonists and antagonists on promethazine-induced anti-plasmid action serve as an indirect evidence of beta adrenergic like binding sites in E. coli. These binding sites are involved in the plasmid replication process and are connected with promethazine binding sites in bacteria.