Dihydropteridine reductase variation in man and the characid fish "Cheirodon axelrodi": evidence for a dimeric enzyme structure.

Genetic evidence for a dimeric structure of dihydropteridine reductase in man and in the fish species "Cheirodon axelrodi" and "Salmo irideus" is presented. A single locus in man and two loci in the fishes examined encode this enzyme. Zymograms revealed two alleles for the locus in man and two alleles for each locus in the fish "Cheirodon axelrodi". The liver homogenate of a patient with dihydropteridine reductase deficiency showed no detectable activity in the gel, while his parents showed the normal electrophoretic phenotype.