Inhibition of Peptide Chain Initiation in Escherichia coli by Hydroxylamine. Reaction of Hydroxylamine with Folate Coenzymes

Previous studies of the means by which hydroxylamine prevents the initiation of peptide synthesis by Escherichia coli extracts have suggested that hydroxylamine interferes with the metabolism of folate coenzymes so as to prevent the formylation of methionyl-tRNA by 10-formyltetrahydrofolate. The possible reactions of hydroxylamine with folate coenzymes and with folate-dependent enzymes have now been examined. Hydroxylamine was found to react with 5,10-methylenetetrahydrofolate but not with other folate coenzymes. One product of the reaction of hydroxylamine with 5,10-methylenetetrahydrofolate was tetrahydrofolate and therefore the other was presumably formaldoxime. Hydroxylamine did not form inhibitory complexes with folate-dependent enzymes. It is concluded that the reaction of hydroxylamine with 5,10-methylenetetrahydrofolate is able to deplete the total intracellular pool of one-carbon folate adducts, including 10-formyltetrahydrofolate, and so to prevent the initiation of peptide synthesis by extracts of such cells.