Forschungsschwerpunkte

Tetrapyrrole biosynthesis in bacteria and archaea

Tetrapyrroles such as hemes, chlorophylls or cobalamin serve as essential cofactors in many proteins and enzymes involved in fundamental biological processes in almost all organisms. For example, hemes and chlorophylls play essential roles during respiration and photosynthesis, whereas cobalamin is the cofactor of many mutases and methyltransferases. The less known tetrapyrroles heme d1 and coenzyme F430 serve as cofactors for key enzymes during denitrification and methanogenesis, respectively. Hemed1 acts as the catalytically essential cofactor for cytochrome cd1 nitrite reductase occurring in many different denitrifying bacteria and thus participates in the maintenance of the global biogeochemical nitrogen cycle. The nickel containing coenzyme F430 serves as cofactor in methyl-coenzyme M reductase, the terminal enzyme during methanogenesis, found in methanogenic archaea. Coenzyme F430 thus plays an important role for the global biogeochemical carbon cycle. All naturally occurring tetrapyrroles are biosynthesized along a branched biosynthetic pathway. The first branchpoint of this pathway occurs at the stage of uroporphyrinogen III representing the first cyclic tetrapyrrole intermediate. Uroporphyrinogen III is decarboxylated to form coproporphyrinogen III directing the pathway toward the formation of hemes in most bacteria and eukaryotes or (bacterio)chlorophylls in photosynthetic bacteria and plants. Alternatively, uroporphyrinogen III is methylated to form precorrin-2 representing the first common intermediate for the biosyntheses of cobalamin, siroheme, heme d1, coenzyme F430 and also heme in the archaea. The formation of cobalamin (anaerobic pathway) and siroheme proceeds via the oxidation of precorrin-2 to sirohydrochlorin and subsequent metal insertion. A minimized version of the branched tetrapyrrole biosynthesis pathway is shown below. Whereas the biosynthetic routes to heme in most bacteria and eukaryotes, to (bacterio)chlorophylls, cobalamin and siroheme are largely understood, the biosyntheses of heme d1 in denitrifying bacteria, of coenzyme F430 in methanogenic archaea and of heme in archaea are still almost completely unknown. The research of our group focuses on the elucidation of the biosynthetic routes leading to these three important tetrapyrrole cofactors.

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letzte Änderung: 30.09.2016

Kontakt

Prof. Dr. Gunhild Layer
Institut für Biochemie
Universität Leipzig
Brüderstraße 34
D-04103 Leipzig

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Telefax: +49 341 97-36919
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Sekretariat
Petra Hartung

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Telefax: +49 341 97-36919
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