Deacon R, Jennings P, Lumb M, Perry J, Purkiss P, Chanarin I
Scand J Haematol. 1981 Oct;27(4):267-70. doi: 10.1111/j.1600-0609.1981.tb00483.x.
Rats were maintained in an atmosphere of equal volumes of oxygen/nitrous oxide (1/1) for up to 7 d and plasma levels of methionine, glycine, serine, histidine, homocysteine and S-methylcysteine were measured. There was a fall in plasma methionine and a rise in plasma serine levels. There were no significant changes in glycine and histidine levels. Homocysteine and S-methylcysteine were not detected in rat plasmas. The fall in plasma methionine was due to loss of cobalamin-dependent methionine synthetase activity. The rise in plasma serine may be due to decline in its metabolism via methenyltetrahydrofolate cyclohydrolase which is concerned in oxidizing the methenyl-carbon ( =CH-), initially derived as a methylene-carbon (-CH2-)from serine, to formate (-CHO).
将大鼠置于等体积氧气/一氧化二氮（1/1）的环境中长达7天，然后测定血浆中甲硫氨酸、甘氨酸、丝氨酸、组氨酸、同型半胱氨酸和S-甲基半胱氨酸的水平。血浆中甲硫氨酸水平下降，丝氨酸水平上升。甘氨酸和组氨酸水平无显著变化。大鼠血浆中未检测到同型半胱氨酸和S-甲基半胱氨酸。血浆中甲硫氨酸水平下降是由于钴胺素依赖性甲硫氨酸合成酶活性丧失。血浆丝氨酸水平上升可能是由于其通过亚甲基四氢叶酸环水解酶的代谢下降，该酶参与将最初从丝氨酸衍生而来的亚甲基碳（-CH2-）氧化为甲酰基碳（=CH-）形成甲酸（-CHO）。
