Purification and characterization of dihydrofolate reductase from methotrexate-resistant human lymphoblastoid cells.

Abstract

Dihydrofolate reductase has been isolated from methotrexate-resistant WIL2 human lymphoblastoid cells. This subline produces ca. 150 times more enzyme than the parental drug-sensitive line. The reductase has been purified to homogeneity by methotrexate affinity chromatography, gel filtration, and preparative isoelectric focusing in a yield of 65%. The enzyme has a pI = 7.7 and a molecular weight of ca. 22000. The amino-terminal 27 amino acid residues have been determined, revealing the location of the single cysteine residue at position 6. Reaction of this cysteine with p-(hydroxy-mercuri)benzoate in the presence of reduced nicotinamide adenine dinucleotide phosphate (NADPH) results in a 5-fold increase in enzyme activity. Other agents including KCl, urea, and thiourea also cause enzyme activation. The Km values for NADPH and dihydrofolate are 0.25 and 0.036 microM, respectively. Mercurial activation of the enzyme results in a 27-fold increase in the Km for NADPH and a 35-fold increase in the Km for dihydrofolate.

Statistics

050100'85'88'91'94'97'00'03'06'09'12'15
Citations per Year

262 Citations

Semantic Scholar estimates that this publication has 262 citations based on the available data.

See our FAQ for additional information.

Cite this paper

@article{Delcamp1983PurificationAC, title={Purification and characterization of dihydrofolate reductase from methotrexate-resistant human lymphoblastoid cells.}, author={Tavner Delcamp and S S Susten and Dale T. Blankenship and James H. Freisheim}, journal={Biochemistry}, year={1983}, volume={22 3}, pages={633-9} }