ENZYME DEFICIENCY IN RED-BLOOD-CELLS IN H UMAN PORPHYRIAS

Hereditary enzyme deficiency in porphyrias can be recognized in blood cells. In the red cell four enzymes of heme biosynthesis can be detect ed: prophobilinogen synthase (delta-aminolevulinic acid dehydrase), ur oporphyrinogen synthase, cosynthase, and decarboxylase. A decrease of prophobilinogen synthase is observed in lead intoxication and in a new type of hereditary acute porphyria with nearly total enzyme dificienc y in the homozygous state with . a residual activity of 1-2 % of contr ols. In another recessive condition, congenital erythropoietic porphyr ia, the deficient uroporphyrinogen cosynthase shows an activity betwee n 1 and 20 %. Acute intermittent porphyria is characterized by diminis hed uroporphyrinogen svnthase which allows the recognition of gene car riers in red cells. In the genetic type of porphyria cutanea tarda tri ggered by alcohol, oral contraceptives, and liver damage the uroporphy rinogen decarboxylase is decreased to about 50 %. In hepatoerythropoie tic porphyria, a homozygous variant of porphyria cutanea tarda, decarb oxylase activity was found below 10 % of controls. With exception of c ongenital erythropoietic, hepatoerythropoietic porphyria, and lead poi soning enzyme deficiencies of porphyrin metabolism in red cells do not lead to anemia.