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Literature summary extracted from

  • Kühner, M.; Haufschildt, K.; Neumann, A.; Storbeck, S.; Streif, J.; Layer, G.
    The alternative route to heme in the methanogenic archaeon Methanosarcina barkeri (2014), Archaea, 2014, 327637.
    View publication on PubMedView publication on EuropePMC

Activating Compound

EC Number Activating Compound Comment Organism Structure
4.1.1.111 Dithionite the haem bound to the AhbA/B complex must be reduced in order for the enzyme to be most active. Treatment with excess dithionite results in a 6.5fold increase in the activity of the enzyme Desulfovibrio desulfuricans
4.1.1.111 Dithionite the heme bound to the AhbA/B complex must be reduced in order for the enzyme to be most active. Treatment with excess dithionite results in a 6.5fold increase in the activity of the enzyme Methanosarcina barkeri

Cloned(Commentary)

EC Number Cloned (Comment) Organism
4.1.1.111 proteins ahbA and ahbB are cloned into distinct plasmids and expressed separately in Escherichia coli. When expressed individually the encoded proteins are highly unstable and can only be purified at very low concentrations due to their tendency to precipitate Desulfovibrio desulfuricans

Crystallization (Commentary)

EC Number Crystallization (Comment) Organism
4.1.1.111 hanging drop vapour diffusion crystallization at 19°C Desulfovibrio desulfuricans

General Stability

EC Number General Stability Organism
4.1.1.111 subunits AhbA and AhbB have a stabilizing effect on each other by forming a complex Desulfovibrio desulfuricans

Inhibitors

EC Number Inhibitors Comment Organism Structure
4.1.1.111 monodecarboxysiroheme single active site with a competitive inhibition model for siroheme and monodecarboxysiroheme Desulfovibrio desulfuricans
4.1.1.111 siroheme single active site with a competitive inhibition model for siroheme and monodecarboxysiroheme Desulfovibrio desulfuricans

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
4.1.1.111 44000
-
 heterodimeric complex of subunits AhbA and AhbB, gel filtration Desulfovibrio desulfuricans
4.1.1.111 94000
-
 heterotetrameric complex of subunits AhbA and AhbB, gel filtration Desulfovibrio desulfuricans

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
4.1.1.111 siroheme Desulfovibrio desulfuricans
-
 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme Methanosarcina barkeri the enzyme is involved in the alternative heme biosynthesis pathway (in bacteria and archaea) 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme Desulfovibrio desulfuricans DSM 6949
-
 12,18-didecarboxysiroheme + 2 CO2
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
4.1.1.111 Desulfovibrio desulfuricans B8J364
-
-
4.1.1.111 Desulfovibrio desulfuricans DSM 6949 B8J364
-
-
4.1.1.111 Methanosarcina barkeri
-
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
4.1.1.111 proteins ahbA and ahbB are cloned into distinct plasmids and expressed separately in Escherichia coli. When expressed individually the encoded proteins are highly unstable and can only be purified at very low concentrations due to their tendency to precipitate Desulfovibrio desulfuricans

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4.1.1.111 siroheme
-
 Methanosarcina barkeri 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme
-
 Desulfovibrio desulfuricans 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme the enzyme is involved in the alternative heme biosynthesis pathway (in bacteria and archaea) Methanosarcina barkeri 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme incubations of individual AhbA and AhbB proteins in excess with sirohaem yields mixtures with varying levels of siroheme, monodecarboxysiroheme and didecarboxysiroheme. The monodecarboxysiroheme is not characterized further and hence it is not determined as to whether it is due to loss of the carboxylic acid from the C12 or C18 side-chain. The individual subunits, AhbA and AhbB, are capable of decarboxylating siroheme by themselves. The individual subunits form homodimers, which likely represents the active species Desulfovibrio desulfuricans 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme
-
 Desulfovibrio desulfuricans DSM 6949 12,18-didecarboxysiroheme + 2 CO2
-
 ?
4.1.1.111 siroheme incubations of individual AhbA and AhbB proteins in excess with sirohaem yields mixtures with varying levels of siroheme, monodecarboxysiroheme and didecarboxysiroheme. The monodecarboxysiroheme is not characterized further and hence it is not determined as to whether it is due to loss of the carboxylic acid from the C12 or C18 side-chain. The individual subunits, AhbA and AhbB, are capable of decarboxylating siroheme by themselves. The individual subunits form homodimers, which likely represents the active species Desulfovibrio desulfuricans DSM 6949 12,18-didecarboxysiroheme + 2 CO2
-
 ?

Subunits

EC Number Subunits Comment Organism
4.1.1.111 heterodimer composed of AhbA and AhbB Methanosarcina barkeri
4.1.1.111 heterodimer the individual subunits, AhbA and AhbB, are capable of decarboxylating sirohaem by themselves. The individual subunits form homodimers, which likely represents the active species. Subunits AhbA and AhbB have a stabilizing effect on each other by forming a complex Desulfovibrio desulfuricans

Synonyms

EC Number Synonyms Comment Organism
4.1.1.111 AhbA/B
-
 Methanosarcina barkeri
4.1.1.111 sirohaem decarboxylase
-
 Methanosarcina barkeri

Cofactor

EC Number Cofactor Comment Organism Structure
4.1.1.111 heme the heme bound to the AhbA/B complex must be reduced in order for the enzyme to be most active. Treatment with excess dithionite results in a 6.5fold increase in the activity of the enzyme Methanosarcina barkeri

General Information

EC Number General Information Comment Organism
4.1.1.111 physiological function the enzyme is involved in the alternative heme biosynthesis pathway (in bacteria and archaea) Desulfovibrio desulfuricans
4.1.1.111 physiological function the enzyme is involved in the alternative heme biosynthesis pathway (in bacterioa and archaea) Methanosarcina barkeri