新規補酵素PQQの化学的機能

抄録

PQQ-oxidation of several substrates such as amines, α-amino acids, alcohols, D-glucose, aldehydes, and thiols is investigated. In the oxidative deamination of amines and the oxidative decarboxylation of α-amino acids, a cationic micelle provides a good environment for the reactions The ionic mechanism via carbinolamine intermediate is proposed for the amine-oxidation. Aluminum t-butoxide and aluminum chloride are found to catalyze the oxidation of alcohols with trimethyl ester of PQQ (PQQTME) D-Glucose and thiols are also oxidized by PQQ efficiently to gluconic acid and the corresponding disulfides, respectively Oxidation of aldehydes by PQQ proceeds efficiently in the presence of a thiazolium salt or cyanide ion. Mechanisms of these reactions are investigated kinetically. An efficient NAD⁺-regeneration system with PQQ and molecular oxygen is found to be applied to HLADH-catalyzed oxidation of alcohols. Finally, synthetic methods of PQQ-model compounds are developed to elucidate the roles of the functional groups of PQQ. The 2-mono- and 2, 9-dicarboxylic acid derivatives 1 b and 1 d and the 1-methylated derivative 1 f are synthesized relatively easily from the intermediates 5 and 4 of the PQQ-synthesis. The 2, 7-dicarboxylic acid derivative 1 e is also synthesized via a combination of the Japp-Klingemann and Fischer indolization.