Mammalian thioredoxin reductases: TR-03 and TR-03B
Mammalian thioredoxin reductase 1 (TrxR) contain an essential seleocycteine residue encoded by the stop codon UGA. This makes recombinant expression in E.coli a challenge. IMCO now has preparations of rat TrxR with unsurpassed specific activity.
The rat TR-03 and TR-03B enzymes show full cross-reactivity with all mammalian thioredoxins as well as other Trx like E.coli Trx1.
For reference see:
Cheng, Q and Arner ESJ : Selenocysteine insertion at a predefined UAG codon in a release factor 1 (RF1)-depleted Escherichia coli host strain bypasses species barriers in recombinant selenoprotein translation. (2017), J. Biol. Chem 292, 5476-5487.
JBC article (pdf, 3086 kB)
NADPH in kits
NADPH is used in the fluorescence kits from IMCO for assay of Trx, Grx or TrxR. Solutions of NADPH are only stable for about 10 days even if stored frozen.
You can make a fresh solution by dissolving 2 mg of NADPH in 0.5 ml of buffer. A solution of NADPH which is turning yellow should be discarded. By making fresh NADPH your assay will work for a long time. Other components of the kits are stable if stored frozen or according to the kit instructions.
Enzymes for assay of Trx1 and TrxR1
The kTRX-01 kit contains 1.2 mg of human Trx1 and 0.15 mg of recombinant fully active selenocysteine-containing TrxR. The kit comes with a description of how to run insulin assy for either thioredoxin or thioredoxin reductase
kTRX-01 (pdf, 140 kB)