Effect of nitrous oxide-induced inactivation of vitamin B12 on glycinamide ribonucleotide transformylase and 5-amino-4-imidazole carboxamide transformylase

Exposure to nitrous oxide (N2O) in vivo is accompanied by oxidation of cobI]-alamin to the inactive cobIII]alamin 1]. There is loss of methionine synthetase activity 2] and evidence of depressed supply of single carbon units at the formate level of oxidation 3,4,5]. We measured the effect of inactivation of B12 on the folate-dependent transformylases concerned in purine synthesis. After 24 h exposure to N2O there was a significant fall in glycinamide ribonucleotide transformylase (EC 2.1.2.2) and a significant increase in 5-amino-4-imidazole carboxamide transformylase (EC 2.1.2.3).