Effect of Vitamin B 12 and Folate on Biosynthesis of Methionine from Homocysteine in the Nematode Caenorhabditis briggsae 1

Abstract

Summary

(i) Omission of L-methionine from the medium resulted in an 80% population reduction. Substitution of D, L-homo-cysteine corrected methionine deficiency in C. briggsae in the presence of supraoptimal vitamin B₁₂ and folic aid.

(ii) An absolute vitamin B₁₂ requirement in C. briggsae developed in the medium containing homocysteine at the second subculture. Concentration of 6 ng/ml of vitamin B₁₂ (at 100 ng/ml of folic acid) was sufficient to support maximum growth of C. briggsae in the medium containing homocysteine.

(iii) It was found that either supraoptimai folic acid (2000 ng/ml) or supraoptimal vitamin B₁₂ (3750 ng/ml), with homocysteine, supported very little population growth of C. briggsae. However, supraoptimal folic acid and supraoptimal vitamin B₁₂ together supported a maximum population growth. Therefore, it was concluded that both vitamin B₁₂ and folic acid were required for the biosynthesis of methionine from homo-cysteine. Studies also showed that the two vitamins spared each other for population growth in the medium containing homocys-teine.