Purification and properties of ferrochelatase from Chironomidae larvae

Ferrochelatase with an M-r of 42,700 Da and a pI of 7.35 has been purified to homogeneity from chironomidae larvae. The activity of the enzyme reached maximum at pH 7.8 and decreased with the increase of pH. The enzyme activi ty varied with temperature and showed maximum activity around 37 degreesC. The purified enzyme was active towards protoporphyrin but inactive towards other porphyrins. The specific enzyme activity of ferrochelatase from chiro nomidae is about 10-fold higher than that of the rat. Electrophoresis of th e purified fractions shows that the enzyme contains only one single polypep tide. The soluble ferrochelatase contained one mole of iron in each mole of the enzyme. The N-terminal sequence analysis of the enzyme shows a high pe rcentage of conserved regions of the enzyme among other species. The enzyme properties are similar to those of the mammalian ferrochelatases except wi th slightly higher specific activity. Chironomidae ferrochelatase appeared to be more heat resistant and less susceptible than its mammalian equivalen t to inhibition by lead.