An interpretation of human diaphorase isozymes in terms of three gene loci DIA1, DIA2 and DIA3

Abstract
NADH and NADPH diaphorase isozymes were studied in human tissues. Evidence from rare heterozygotes suggests that the red cell and main tissue forms of NADH diaphorase are products of the same locus, DIA1, NADPH-dependent diaphorase appears to be the product of a 2nd locus DIA2. A 3rd locus, DIA3, codes for the polymorphic sperm diaphorase. The products of this locus are also found in fetal tissues, placenta and adult brain and gonads. The products of these 3 loci may be distinguished by their substrate specificity, thermostability and molecular size.