The Isolation and Characterization of Dihydropteridine Reductase from Sheep Liver

Abstract

Abstract Dihydropteridine reductase has been obtained from sheep liver in essentially homogeneous form. The enzyme exists as a dimer of molecular weight 41,000 to 42,800. The subunit molecular weight has been determined to be 21,300. In the presence of the quinonoid tautomer of either dihydrobiopterin or dihydro-6, 7-dimethylpterin, DPNH is a better substrate than TPNH. Evidence indicates that the activity of this enzyme is far greater than that of the known pterindependent hydroxylases in all tissues examined.