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Publication Abstract from PubMed

The acid induced arginine decarboxylase is part of an enzymatic system in Escherichia coli that contributes to making this organism acid resistant. The arginine decarboxylase is a vitamin B6-dependent enzyme that is active at acidic pH. It consumes a proton in the decarboxylation of arginine to agmatine and by working in tandem with an arginine-agmatine antiporter this enzymatic cycle protects the organism by preventing the accumulation of protons inside the cell. We have determined the structure of the acid induced arginine decarboxylase by X-ray crystallography to 2.4 A resolution. The arginine decarboxylase structure, revealed a ca. 800 kDa decamer composed as a pentamer of five homodimers. Each homodimer has an abundance of acidic surface residues, which at neutral pH prevent inactive homodimers from associating into active decamers. Conversely, acidic conditions favor the assembly of active decamers. Therefore, the structure of arginine decarboxylase presents a mechanism by which its activity is modulated by external pH.

Crystal Structure of the Acid Induced Arginine Decarboxylase from Escherichia coli: Reversible Decamer Assembly Controls Enzyme Activity.,Andrell J, Hicks M, Palmer T, Carpenter E, Iwata S, Maher M Biochemistry. 2009 Mar 19. PMID:19298070^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.