102] Preparation of an antiserum to sheep liver dihydropteridine reductase

Abstract

Publisher Summary This chapter discusses the preparation of an antiserum to sheep liver dihydropteridine reductase. The classic form of the genetic disease, phenylketonuria, has been characterized as being due to the absence of hepatic phenylalanine hydroxylase activity. A case of hyperphenylalaninemia was found, with adequate amounts of hepatic phenylalanine hydroxylase activity, but lacking any dihydropteridine reductase activity. To further characterize the enzymic defect in dihydropteridine reductase deficiency, an antiserum to dihydropteridine reductase was prepared. Dihydropteridine reductase was purified from human liver, but it is more conveniently and easily purified from sheep liver. It was found that the antiserum cross-reacts, with dihydropteridine reductase, from sheep, cow, rat, and humans. In addition, a single precipitin line of identity, by immunodiffusion on ouchterlony plates is also discussed, with dihydropteridine reductase, purified from bovine liver, kidney, brain, and adrenal glands. By immunotitration, 1 ml of antiserum neutralizes 100% of the dihydropteridine reductase activity in 2.5 g of sheep liver, 0.5 g of rat liver, or 1 g of human liver. In contrast to the results, with normal human liver, no precipitin line was obtained when the antiserum was tested on ouchterlony plates against a liver extract prepared from a patient, with hyperphenylalaninemia, due to the deficiency of dihydropteridine reductase.