Protoporphyrinogen oxidase and ferrochelatase in porphyria variegata

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Abstract
Protoporphyrinogen oxidase activity and ferrochelatase activity were measured in leukocytes from patients with porphyria variegata. The mean activity of protoporphyrinogen oxidase (PPO) in porphyria variegata (PV) was about 50% of normal (P < 0.05). The mean activity of ferrochelatase with 59Fe2+ sulfate and protoporphyrin as substrates (in the presence of ascorbic acid) was reduced by 40% (P < 0.009). The mean activity of ferrochelatase with 59Fe3+ chloride and protoporphyrin as substrates (in the presence of reduced glutathione) was increased by 65% (P < 0.005). Both are statistically highly significant. The findings are interpreted as follows: (a) The occurrence of a low level of protoporphyrinogen oxidase in PV is confirmed. (b) The findings indicate a concurrent structural change in ferrochelatase (this may be structurally related to (a) but no evidence of this is at present available).