Methylenetetrahydrofolate reductase in the rat central nervous system: Intracellular and regional distribution

摘要: Abstract Methylenetetrahydrofolate reductase and methyltetrahydrofolate-homocysteine methyltransferase were found to be localized in the soluble fraction of rat brain. They are clearly separated from serine hydroxymethyltransferase glycine cleavage complex which mitochondria this tissue. Hence, although primary, if not only, site 5,10-methylenetetrahydrofolate formation brain appears mitochondrion, utilization compound for 5-methyltetrahydrofolate synthesis latter methylation homocysteine occurs cytosol. Parallel experiments with liver confirmed that tissue also fraction, while is about evenly divided between However, (but brain) activity supernatant only partially expressed unless dialyzed. We have phenomenon, initially suggested occurrence an endogenous inhibitor extracts [Ordonez Wurtman (1973) J. Neurochem., 21, 1447–1455] , due loss product (5, 10-methyl-enetetrahydrofolate) assay via its oxidation by methylenetetrahydrofolate dehydrogenase, combination NADP present undialyzed extracts. All regions central nervous system tested contained activity. Regional variations observed however, almost threefold difference specific activities highest lowest ranking Comparison rank order 12 respect (this study) methyltetrahydrofolate-tryptamine N-methyltransferase [Mandell, Knapp, Hsu (1974) Life Sci., 14, 1–17] shows a high positive correlation (r = 0.916) these selected regions.