Residues involved in the mechanism of the bifunctional methylenetetrahydrofolate dehydrogenase-cyclohydrolase: the roles of glutamine 100 and aspartate 125

The Journal of Biological Chemistry
Saravanan Sundararajan, R E MacKenzie

Abstract

The human bifunctional dehydrogenase-cyclohydrolase domain catalyzes the interconversion of 5,10-methylene-H(4)folate and 10-formyl-H(4)folate. Although previous structure and mutagenesis studies indicated the importance of lysine 56 in cyclohydrolase catalysis, the role of several surrounding residues had not been explored. In addition to further defining the role of lysine 56, the work presented in this study explores the functions of glutamine 100 and aspartate 125 through the use of site-directed mutagenesis and chemical modification. Mutants at position 100 are inactive with respect to cyclohydrolase activity while preserving significant dehydrogenase levels. We succeeded in producing a K56Q/Q100K double mutant, which has no cyclohydrolase yet retains more than two-thirds of wild type dehydrogenase activity. Neither activity is detectable in aspartate 125 mutants with the exception of D125E. The results indicate that the function of glutamine 100 is to activate lysine 56 for cyclohydrolase catalysis and that aspartate 125 is involved in the binding of the H(4)folate substrates. In highlighting the importance of these residues, catalytic mechanisms are proposed for both activities as well as an explanation for the differenc...Continue Reading

References

Aug 1, 1975·Archives of Biochemistry and Biophysics·E J DruryR E MacKenzie
Jul 1, 1992·Proceedings of the National Academy of Sciences of the United States of America·R J AlmassyZ Hostomska
Sep 16, 1981·Biochemical and Biophysical Research Communications·M D BondH E Van Wart
Nov 1, 1983·Canadian Journal of Biochemistry and Cell Biology = Revue Canadienne De Biochimie Et Biologie Cellulaire·D DrummondR E MacKenzie

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Citations

Aug 16, 2005·The Journal of Biological Chemistry·Karen E ChristensenRobert E Mackenzie
Dec 6, 2019·Medicinal Research Reviews·Miyanou Rosales-HurtadoZohra Benfodda
Sep 22, 2021·Proceedings of the National Academy of Sciences of the United States of America·Danielle E AndersonXu Tan

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