MetaCyc Compound: ferroheme b

Synonyms: protoheme IX, ferroprotoporphyrin IX

Superclasses: a macrocyclea porphyrinhemeheme b
an organometallic compoundheme b

'Heme' is usually understood as any tetrapyrrolic chelate of iron. The terms 'ferroheme' and 'ferriheme' refer to the Fe(II) and Fe(III) oxidation states in heme (even though Fe(IV) is found as a catalytic intermediate in some systems).

Heme b, whose ferrous form is known as protoheme IX, is the immediate product of the heme biosynthesis pathways (by ferro-chelation of protoporphyrin IX) and the most abundant heme form. It is found in common proteins such as hemoglobin and myoglobin.

Heme b is part of b-type cytochromes.

Chemical Formula: C34H30N4O4Fe

Molecular Weight: 614.48 Daltons

Monoisotopic Molecular Weight: 616.1772976364 Daltons

ferroheme <i>b</i> compound structure

SMILES: C=CC1(C(C)=C7(C=C8(C(C)=C(CCC(=O)[O-])C6(=[N+]([Fe--]24(N(C=1C=C3(C(C)=C(C=C)C(=[N+]23)C=C5(C(C)=C(CCC(=O)[O-])C(N45)=C6)))7))8))))

InChI: InChI=1S/C34H34N4O4.Fe/c1-7-21-17(3)25-13-26-19(5)23(9-11-33(39)40)31(37-26)16-32-24(10-12-34(41)42)20(6)28(38-32)15-30-22(8-2)18(4)27(36-30)14-29(21)35-25;/h7-8,13-16H,1-2,9-12H2,3-6H3,(H4,35,36,37,38,39,40,41,42);/q;+2/p-4/b25-13-,26-13-,27-14-,28-15-,29-14-,30-15-,31-16-,32-16-;


Standard Gibbs Free Energy of Change Formation (ΔfG in kcal/mol): 277.38635Inferred by computational analysis [Latendresse13]

Reactions known to consume the compound:

heme degradation , phycocyanobilin biosynthesis , phycoerythrobilin biosynthesis I , phycoerythrobilin biosynthesis II , phycourobilin biosynthesis , phycoviolobilin biosynthesis , phytochromobilin biosynthesis :
ferroheme b + 3 a reduced [NADPH-hemoprotein reductase] + 3 oxygen + 2 H+ → biliverdin-IX-α + Fe2+ + carbon monoxide + 3 an oxidized [NADPH-hemoprotein reductase] + 3 H2O

Not in pathways:
ferroheme b + 4 an reduced unknown electron acceptor + 4 oxygen + 2 H+ → 5-oxo-δ-bilirubin + Fe2+ + carbon monoxide + 4 an oxidized unknown electron acceptor + 4 H2O
ferroheme b + 4 an reduced unknown electron acceptor + 4 oxygen + 2 H+ → 15-oxo-β-bilirubin + Fe2+ + carbon monoxide + 4 an oxidized unknown electron acceptor + 4 H2O

Reactions known to produce the compound:

heme biosynthesis III (from siroheme) :
Fe-coproporphyrin III + 2 S-adenosyl-L-methionine → ferroheme b + 2 CO2 + 2 5'-deoxyadenosine + 2 L-methionine

Reactions known to both consume and produce the compound:

heme biosynthesis I (aerobic) , heme biosynthesis II (anaerobic) , superpathway of heme biosynthesis from uroporphyrinogen-III :
protoporphyrin IX + Fe2+ferroheme b + 2 H+

Not in pathways:
heme b + (2E,6E)-farnesyl diphosphate + H2O ↔ heme o + diphosphate

In Reactions of unknown directionality:

Not in pathways:
heme b + hydrogen peroxide = heme d

In Transport reactions:
ferroheme b[cytosol] + ATP + H2O → ferroheme b[periplasm] + ADP + phosphate + H+,
heme b[cytosol] + ATP + H2O ↔ heme b[periplasm] + ADP + phosphate + H+

Enzymes inhibited by ferroheme b, sorted by the type of inhibition, are:

Inhibitor (Noncompetitive) of: 5-aminolevulinate synthase [Burnham63, Jordan86] Inhibitor (Mechanism unknown) of: ferrochelatase [Dailey86a]

This compound has been characterized as a cofactor or prosthetic group of the following enzymes: formate dehydrogenase N, succinate:quinone oxidoreductase, ubiquinol oxidase (H+-transporting), cytochrome bd-I terminal oxidase, hydrogen:menaquinone oxidoreductase, hydroperoxidase, catalase, dihydropteridine reductase, nitric oxide dioxygenase

Created 21-Aug-2014 by Caspi R, SRI International


Burnham63: Burnham B. F., Lascelles J. (1963). "Control of porphyrin biosynthesis through a negative-feedback mechanism." Biochem. J. 87, 462-472.

Dailey86a: Dailey HA (1986). "Purification and characterization of bacterial ferrochelatase." Methods Enzymol 123;408-15. PMID: 3702737

Jordan86: Jordan PM, Laghai-Newton A (1986). "Purification of 5-aminolevulinate synthase." Methods Enzymol 123;435-43. PMID: 3702741

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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