N 5 -Methyltetrahydrofolate-Homocysteine Cobalamin Methyltransferase Activity in Chronic Erythremic Myelosis (Di Guglielmo Syndrome) 1

Summary

Activity of N⁵-methyltetrahy-drofolate-homocysteine cobalamin methyl-transferase was determined in sonicates of bone marrow obtained from five patients with chronic erythremic myelosis (Di-Guglielmo syndrome), three patients with severe untreated pernicious anemia, and eight normal persons. In four of the five patients with chronic erythremic myelosis, enzymatic activity was higher than in normals, and addition of methylcobalamin did not affect enzymatic activity, suggesting that the enzyme exists as the holomethyltransfer-ase. Increasing essential substrates such as S-adenosylmethionine, homocysteine, and methyltetrahydrofolate to fourfold the level used in the standard assay did not affect enzymatic activity significantly. Increased activity of this enzyme in chronic erythremic myelosis may relate to the high proliferative capacity reflected by increased cell turnover and intramedullary cell death.