Effect of Vitamin B12 and Folate on Biosynthesis of Methionine from Homocysteine in the Nematode Caenorhabditis briggsae

Abstract

The roles of dietary vitamin B12 and folic acid in methionine biosynthesis from homocysteine were first observed in higher animals. Jukes, Stokstad, and Broquist (1) noted that the growth of vitamin BIZ-deficient chicks was increased by either methionine or homocysteine and vitamin B,, but not by homocysteine alone. It was also reported that rats were able to utilize homocysteine in lieu of methionine when folic acid (2) or choline (3) was added to the diet. In microorganisms, Escherichia coli is known to possess two alternative pathways for methionine biosynthesis: the vitamin B,,-dependent pathway (4) and the vitamin BIZ-independent one ( 5 ) . In the present study, we show evidence that dietary vitamin Blz and folic acid are required for the biosynthesis of methionine from homocysteine in an axenic free-living nematode, Caenorhabditis briggsae . Information related to biochemical nutrition in invertebrates is sparse. Therefore, this study has particular relevance to the fields of comparative nutrition and biochemistry.Materials and methods. Composition of the basal medium. The chemical-defined medium Caenorhabditis briggsae maintenance medium (CbMM) (6) was specially prepared by the Grand Island Biological Company (Grand Island, New York) and supplied as a sterile, double-strength solution. Several of those chemical components which are normally present in the standard medium were deleted from the special medium: vitamin BIZ, folic acid, calcium folinate (5-formyltetrahydrofolic acid), L-methionine, choline dihydrogen citrate , gluta-

Lack of heme synthesis in a free-living eukaryote

“…1C). Cytochrome c or hemoglobin also sustained worm growth, supporting previous studies that have shown heme and vitamin B12, another tetrapyrrole, as necessary factors for C. briggsae development (8,9,34). Our observations that worms can develop to the L4 stage in the absence of exogenous heme in the growth medium suggest that either there are trace amounts of heme in the medium or, more plausibly, maternal heme stored in the egg during embryogenesis is able to sustain early larval growth.…”

Metabolic Fate of Cyanocobalamin Taken up by Spirometra mansonoides Spargana

“…From these results we conclude that no methyltransferase enzyme occurs in spargana of S. mansonoides. The absence of methyltransferase activity in both A. suum and the cat ascarid provides an interesting contrast with the findings of Lu et al (1976). These investigators have presented presumptive evidence for the presence of the methyltransferase enzyme in the free-living nematode, Caenorhabditis briggsae.…”

Biochemical Impedance on Intracellular Functions of Vitamin B12 in Chronic Toxigenic Mold Exposures

“…The metabolism and intracellular recycling of methionine requires vitamin B12 as cofactor and methyltetrahydrofolate as co-reactant [27,28,29]. In fact, both vitamin B12 and folic acid are required for the biosynthesis of methionine from homocysteine [30]. The beneficial effects of folate in the above conditions can be explained largely within the context of folate-dependent pathways, such as methionine, purine and pyrimidine biosynthesis [31].…”