Porphobilinogen deaminase and the synthesis of porphyrin isomers in the Dubin-Johnson syndrome.

Porphyrin synthesis was studied in a family of 9.3 of whom had the Dubin-Johnson syndrome (DJS). Subjects with DJS had modest increases in urinary porphyrin concentration with a marked increase in the series I isomer of coproporphyrin (tetracarboxylic) as well as in the octa-, hepta-, hexa- and penta-carboxyl porphyrins. Activity of erythrocyte porphobilinogen deaminase (PBG-D) was also increased. Non-expressing carriers in the family had normal levels of urinary porphyrins but modest increases in both series I isomer accumulation and PBG-D activity. These results may provide a rationale for the altered synthesis of porphyrin in DJS.