Ferrochelatase activity in Azospirillum brasilense with reference to the influence of metal cations.
Ferrochelatase in membrane preparations from Azospirillum brasilense displayed an activity of 2.17 mumol protoheme formed.h-1.mg protein-1 which is 10-fold greater than previous reports for other bacteria. This ferrochelatase showed an apparent Km of 20.9 microM for Fe2+, a pH optimum of 6.0-6.5, and stimulation by oleic or stearic acids. Co2+, Cu2+ and Zn2+ inhibited the incorporation of Fe2+ into protoporphyrin IX while Ni2+ and Mg2+ had no effect on protoheme synthesis. Activity with Fe2+ and mesoporphyrin IX was less than with protoporphyrin IX but deuteroporphyrin IX produced the highest rate of protoheme synthesis. The membrane fraction containing ferrochelatase activity was found to insert Cu2+, Ni2+, Zn2+ and Co2+ enzymatically into protoporphyrin IX to produce metalloporphyrins. Cu2+ incorporation into protoporphyrin IX proceeded at a rate greater than with Fe2+ and the Km for Cu2+ was 21.9 microM.
Price
M J
MJ
Department of Biology, University of New Mexico, Albuquerque 87131.
Saiz
B L
BL
Barton
L L
LL
D015806:Azospirillum brasilense / Q000201:enzymology*; D002413:Cations, Divalent / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005294:Ferrochelatase / Q000378:metabolism*; D006418:Heme / Q000096:biosynthesis; D008670:Metals / Q000378:metabolism*; D013379:Substrate Specificity
D002413:Cations, Divalent; D005227:Fatty Acids; D008670:Metals; D006418:Heme; D005294:Ferrochelatase