Multiple forms of L1210 dihydrofolate reductase differing in affinity for methotrexate.
Dihydrofolate reductase, purified from a Methotrexate-resistant subline (R6) of L1210 mouse leukemia cells, consists of two forms (designated 1 and 2) differing in affinity for the drug. Form 1 is more sensitive to inhibition by Methotrexate. Form 2 is more heat-labile, but it can be stabilized by bovine serum albumin or NADPH. Isoelectric focusing resolves 1 and 2; pI values are 7.4 and 8.2. Forms 1 and 2 comprise about 10 and 90% of the total protein, but 1 has at least a 2-fold higher specific activity. Binding measurements with [3H]Methotrexate provide KD values of ca. 1 and 27 nM for 1 and 2.
D000818:Animals; D004355:Drug Stability; D006358:Hot Temperature; D007526:Isoelectric Point; D007939:Leukemia L1210 / Q000201:enzymology*; D008727:Methotrexate / Q000378:metabolism*; D051379:Mice; D013379:Substrate Specificity; D013762:Tetrahydrofolate Dehydrogenase / Q000302:isolation & purification* / Q000378:metabolism
D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate