Dihydrofolate reductase (DHFR) is a member of the reductase family of enzymes that is ubiquitously expressed in all organisms. DHFR catalyzes the NADPH-dependent reduction of dihydrofolate to tetrahydrofolate, and it is essential for the synthesis of thymidylate, purines and several amino acids. Expression of methotrexate (MTX)- resistant variants of DHFR in normal hematopoietic cells is a potential strategy to permit administration of larger doses of MTX by alleviating drug toxicity in normal cells and tissues that are drug sensitive. Source: Recombinant protein corresponding to aa1-187 from mouse DHFR, fused to His-tag at N-terminal expressed in E. coli. Molecular Weight: ~23.6kD (207aa) Specific Activity: >2000pmol/min/ug, and is defined as the amount of enzyme that converts 1pmole of dihydrofolic acid to tetrahydrofolic acid/minute at pH 6.5 at 25C. Amino Acid Sequence: MGSSHHHHHH SSGLVPRGSH MVRPLNCIVA VSQNMGIGKN GDLPWPPLRN EFKYFQRMTT TSSVEGKQNL VIMGRKTWFS IPEKNRPLKD RINIVLSREL KEPPRGAHFL AKSLDDALRL IEQPELASKV DMVWIVGGSS VYQEAMNQPG HLRLFVTRIM QEFESDTFFP EIDLGKYKLL PEYPGVLSEV QEEKGIKYKF EVYEKKD Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 6 months after receipt at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.