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Biochim Biophys Acta. 2001 May 1;1505(1):15-27.

Sodium ion-translocating decarboxylases.

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  • Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, D-35032, Marburg, Germany. buckel@mailer.uni-marburg.de

Abstract

The review is concerned with three Na(+)-dependent biotin-containing decarboxylases, which catalyse the substitution of CO(2) by H(+) with retention of configuration (DeltaG degrees '=-30 kJ/mol): oxaloacetate decarboxylase from enterobacteria, methylmalonyl-CoA decarboxylase from Veillonella parvula and Propiogenium modestum, and glutaconyl-CoA decarboxylase from Acidaminococcus fermentans. The enzymes represent complexes of four functional domains or subunits, a carboxytransferase, a mobile alanine- and proline-rich biotin carrier, a 9-11 membrane-spanning helix-containing Na(+)-dependent carboxybiotin decarboxylase and a membrane anchor. In the first catalytic step the carboxyl group of the substrate is converted to a kinetically activated carboxylate in N-carboxybiotin. After swing-over to the decarboxylase, an electrochemical Na(+) gradient is generated; the free energy of the decarboxylation is used to translocate 1-2 Na(+) from the inside to the outside, whereas the proton comes from the outside. At high [Na(+)], however, the decarboxylases appear to catalyse a mere Na(+)/Na(+) exchange. This finding has implications for the life of P. modestum in sea water, which relies on the synthesis of ATP via Delta(mu)Na(+) generated by decarboxylation. In many sequenced genomes from Bacteria and Archaea homologues of the carboxybiotin decarboxylase from A. fermentans with up to 80% sequence identity have been detected.

PMID:
11248185
[PubMed - indexed for MEDLINE]
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