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Synthesis and crystal structure of pyrroloquinoline quinol (PQQH 2 ) and pyrroloquinoline quinone (PQQ)
Author(s) -
Ikemoto Kazuto,
Mori Shigeki,
Mukai Kazuo
Publication year - 2017
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520617002281
Subject(s) - pyrroloquinoline quinone , chemistry , cofactor , aldehyde , alcohol , crystal structure , quinone , stereochemistry , organic chemistry , catalysis , enzyme
Pyrroloquinoline quinone (PQQ) is a water‐soluble quinone compound first identified as a cofactor of alcohol‐ and glucose‐dehydrogenases (ADH and GDH) in bacteria. For example, in the process of ADH reaction, alcohol is oxidized to the corresponding aldehyde, and inversely PQQ is reduced to pyrroloquinoline quinol (PQQH 2 ). PQQ and PQQH 2 molecules play an important role as a cofactor in ADH and GDH reactions. However, crystal structure analysis has not been performed for PQQ and PQQH 2 . In the present study, the synthesis of PQQH 2 powder crystals was performed under air, by utilizing vitamin C as a reducing agent. By reacting a trihydrate of disodium salt of PQQ (PQQNa 2 ·3H 2 O) with excess vitamin C in H 2 O at 293 and 343 K, yellowish brown and black powder crystals of PQQH 2 having different properties were obtained in high yield, respectively. The former was PQQH 2 trihydrate (PQQH 2 ·3H 2 O) and the latter was PQQH 2 anhydrate (PQQH 2 ). Furthermore, sodium‐free red PQQ powder crystal (a monohydrate of PQQ, PQQ·H 2 O) was prepared by the reaction of PQQNa 2 ·3H 2 O with HCl in H 2 O. Single crystals of PQQH 2 and PQQ were prepared from Me 2 SO/CH 3 CN mixed solvent, and we have succeeded in the crystal structure analyses of PQQH 2 and PQQ for the first time.