1: With ethylenediaminetetraacetic acid; 1,4-dithio-DL-threitol; uroporphyrinogen decarboxylase in phosphate buffer; water T=37°C; pH=6.8; 2: With ethylenediaminetetraacetic acid; 1,4-dithio-DL-threitol; uroporphyrinogen decarboxylase in phosphate buffer; water T=37°C; 3: With ethylenediaminetetraacetic acid; 1,4-dithio-DL-threitol; uroporphyrinogen decarboxylase in phosphate buffer; water T=37°C; Further stages.;