Details

Autor(en) / Beteiligte

• Blom, C.
• Klasen, E.C.
• Van Steveninck, J.

Titel

Different characteristics of ferrochelatase in cultured fibroblasts of erythropoietic protoporphyria patients and normal controls

Ist Teil von

• Biochimica et biophysica acta, 1990-07, Vol.1039 (3), p.339-342

Ort / Verlag

Netherlands: Elsevier B.V

Erscheinungsjahr

1990

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• Ferrochelatase activity was measured in crude extracts of fibroblasts, obtained from erythropoietic protoporphyria patients and healthy controls. The enzyme activity in erythropoietic protoporphyria fibroblasts was about 50% lower, compared to the controls. The sulfhydryl-oxiding reagent diamide inhibited the normal enzyme by about 50%, whereas ferrochelatase from erythropoietic protoporphyria fibroblasts was completely insensitive to the reagent. Pb 2+ inhibits ferrochelatase activity by reacting with essential sulfhydryl groups. Low concentrations of Pb 2+ inhibited the normal enzyme by 56%, but the mutant enzyme by only 8%. The photodynamic activity of bound mesoporphyrin substrate caused a biphasic inactivation of the normal enzyme.During the first 5 min of illumination a fast decrease of enzyme activity occured to about 60% of the initial value. Experimental evidence indicates that this first phase of inactivation is caused by photooxidation of sulfhydryl groups. Durings further illumination inactivation continued at a much slower rate. With ferrochelatase from erythropoitic protoporphyria fibroblasts only the second, slow phase of photodynamic inactivation was observed. These observations suggest a mutation of ferrochelatase in erythropoietic proporphyria, affecting the reactivity of sulfhydryl groups, involved in the catalytic of activity of the enzyme.