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Crystal structure of a calcium(II)-pyrroloquinoline quinone (PQQ) complex outside a protein environment
Henning Lumpe1, Peter Mayer1, Lena J Daumann1
1Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Munich, Bavaria 81377, Germany.
Abstract:
Pyrroloquinoline quinone (PQQ) is an important cofactor of calcium- and lanthanide-dependent alcohol dehydrogenases, and has been known for over 30 years. Crystal structures of Ca-MDH enzymes (MDH is methanol dehydrogenase) have been known for some time; however, crystal structures of PQQ with biorelevant metal ions have been lacking in the literature for decades. We report here the first crystal structure analysis of a Ca-PQQ complex outside the protein environment, namely, poly[[undecaaquabis(μ-4,5-dioxo-4,5-dihydro-1H-pyrrolo[2,3-f]quinoline-2,7,9-tricarboxylato)tricalcium(II)] dihydrate], {[Ca3(C14H3N2O8)2(H2O)11]·2H2O}n. The complex crystallized as Ca3PQQ2·13H2O with Ca2+ in three different positions and PQQ3-, including an extensive hydrogen-bond network. Similarities and differences to the recently reported structure with biorelevant europium (Eu2PQQ2) are discussed.
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