Porphyrin-substrate binding to murine ferrochelatase: effect on the thermal stability of the enzyme.

ABSTRACT: Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the haem biosynthetic pathway, catalyses the chelation of Fe(II) into the protoporphyrin IX ring. The energetics of the binding between murine ferrochelatase and mesoporphyrin were determined using isothermal titration calorimetry, which revealed a stoichiometry of one molecule of mesoporphyrin bound per protein monomer. The binding is strongly exothermic, with a large intrinsic enthalpy (DeltaH=-97.1 kJ x mol(-1)), and is associated with the uptake of two protons from the buffer. This proton transfer suggests that hydrogen bonding between ferrochelatase and mesoporphyrin is a key factor in the thermodynamics of the binding reaction. Differential scanning calorimetry thermograms indicated a co-operative two-state denaturation process wit

SUBMITTER: Franco R 

PROVIDER: S-EPMC1134880 | biostudies-literature | 2005 Mar

REPOSITORIES: biostudies-literature