No effect of hyperbaric oxygen on methionine synthetase activity in rats

Nitrous oxide is the only anesthetic gas or vapor known to inactivate the vitamin B12 cofactor of the enzyme methionine synthetase. However, there are conflicting reports on whether oxygen at one atmosphere has any effect. The authors found that the hepatic methionine synthetase activity of Sprague-Dawley rats was unchanged after 4 h exposure to two atmospheres of oxygen.