Dissociation of methionine synthetase (EC 2.1.1.13) activity and impairment of DNA synthesis in fruit bats (Rousettus aegyptiacus) with nitrous oxide-induced vitamin B12 deficiency.
1. The effect of methylcobalamin inactivation by the anaesthetic gas nitrous oxide on the activity of the cobalamin-dependent methionine synthetase (5-methyltetrahydrofolate homocysteine methyltransferase; EC 2.1.1.13) reaction, and on DNA synthesis, in the fruit bat Rousettus aegyptiacus, was examined. 2. Methionine synthetase activity in the liver of bats exposed to N2O-oxygen (50:50, v/v) for 90 min/d averaged 32% of that of controls after 4 d of exposure and only 5% after 12-14 weeks of exposure. 3. DNA synthesis in the bone marrow, as reflected by the deoxyuridine suppression test, was unaffected by 4 d of exposure to N2O and only minimally affected after 5-10 weeks of exposure. 4. These results suggest that DNA synthesis in the fruit bat is unusually resistant to inhibition of methionine synthetase and imply the existence of a non-methylated circulating folate pool in this species.
van Tonder
S V
SV
Department of Haematology, School of Pathology, South African Institute for Medical Research, Johannesburg.
Ruck
A
A
van der Westhuyzen
J
J
Fernandes-Costa
F
F
Metz
J
J
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000378:metabolism*; D000818:Animals; D002685:Chiroptera / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D008780:Methyltransferases / Q000378:metabolism*; D009609:Nitrous Oxide / Q000633:toxicity*; D014805:Vitamin B 12 / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors; D014806:Vitamin B 12 Deficiency / Q000139:chemically induced*
D004247:DNA; C019476:mecobalamin; D008780:Methyltransferases; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D009609:Nitrous Oxide; D014805:Vitamin B 12