Description_x000D_ General description_x000D_ Human DHFR is an 186 amino acid protein with an apparent molecular weight of 25 kDa. It is 30% homologous to the E. coli protein and up to 70% homologous to vertebrate proteins._x000D_ Application_x000D_ Dihydrofolate Reductase human has been used:_x000D_ • to investigate the stable expression of green fluorescent protein and the targeted disruption of thioredoxin peroxidase-1 gene in Babesia bovis_x000D_ • to study the structural analysis of human dihydrofolate reductase as a binary complex_x000D_ • to study its in vitro kinetic assay for the enzyme inhibition study_x000D_ Packaging_x000D_ 0.25 unit in glass bottle_x000D_ Biochem/physiol Actions_x000D_ Dihydrofolate reductase (DHFR) is a key enzyme in thymidine synthesis. It catalyzes the reduction of dihydrofolate (DHF) to tetrahydrofolate (THF). At a much lower rate, it catayzes the conversion of folate to THF. Since thymidine is a necessary substrate for DNA synthesis, DHFR is a target for anticancer drug development. Methotrexate is the prototype dihydrofolate reductase inhibitor. The enzyme from Sigma has been used in the inhibitory studies of Leishmaniasis donovani pteridine reductase 1 (PTR1). The enzyme has also been used as a positive control to measure the DHFR activity of a protein, MS0308, purified from Mycobacterium smegmatis._x000D_ Km5,6_x000D_ NADPH 0.16 mM_x000D_ 7,8-dihydrofolate 0.03 mM_x000D_ 8-methylpterin 0.13 mM_x000D_ Ki7_x000D_ Folate 2.6x10-5 mM_x000D_ Methotrexate 6.1-9x10-9_x000D_ The human DHFR gene, as well as DHFR genes in other mammalian species, overcome the inhibitory effects of methotrexate by a mechanism of gene amplification or by amino-acid mutagenesis. Dihydroflate reductase (DHFR) catalyzes the NADPH dependent reduction of dihydrofolate (DHF) to tetrahydrofolate (THF) and, at a much lower rate, the conversion of folate to THF. The reaction product, THF, is an essential cofactor in the conversion of deoxyuridylate (dUMP) to deoxythymidylate (dTMP) by thymidylate synthetase. It is a key enzyme in thymidine synthesis. Therefore, DHFR is a critical enzyme in DNA synthesis and has become a target for drug development and cancer therapy. The variations between DHFR from different sources have enabled the development of species selective DHFR inhibitors, such as trimethoprim (antibacterial and antifungal), pyrimethamine (antiprotozoal), and methotrexate; MTX (antineoplastic, antipsoriatic, and anti-inflammatory)._x000D_ Unit Definition_x000D_ One unit will convert 1.0 μmole of dihydrofolic acid to tetrahydrofolic acid in 1 minute at pH 7.5 at 22 °C._x000D_ Physical form_x000D_ Solution in 10 mM Tris pH 8, 1 mM EDTA, 0.5 mM DTT, 5 μM NADPH, protease inhibitors, and 50% glycerol.