INHIBITION OF REDOX CYCLING OF METHOXATIN (PQQ) AND OF SUPEROXIDE RELEASE BY PHAGOCYTIC WHITE CELLS

The iodonium compounds diphenyleneiodonium and diphenyliodonium, and t he amine compounds, 4,5-dimethyl phenylene diamine, N,N-dimethyl 1,4-p henylene diamine, 1,2-diamino-4,5-methyleneoxybenzene, and aminomalono nitrile inhibit methoxatin's (PQQ's) redox activity in vitro, that is, the methoxatin-coupled oxidation of glycine and reduction of nitroblu e tetrazolium to formazan. The compounds mentioned above also inhibit phorbol myristate acetate (PMA) stimulated superoxide release by phago cytic white cells-determined mainly as the superoxide dismutase sensit ive reduction of ferricytochrome C. Related compounds, 3,4-diaminopyri dine and 4-dimethylamino-benzylamine, did not inhibit redox activity o f PQQ in vitro, nor did they inhibit PMA stimulated superoxide product ion in monocytes or neutrophils. Thus, there is a correlation between an agent's ability to inhibit PQQ redox cycling and its ability to inh ibit superoxide release by phagocytes. The findings are a further indi cation that PQQ is involved in the respiratory burst of phagocytic cel ls.