Sugioka K, Nakano M, Naito I, Tero-Kubota S, Ikegami Y
College of Medical Care and Technology, Gunma University, Japan.
Biochim Biophys Acta. 1988 Feb 17;964(2):175-82. doi: 10.1016/0304-4165(88)90164-x.
The oxidation of NAD(P)H by pyrroloquinoline quinone (PQQ) was non-enzymatically carried out at physiological pH in the presence of O2. The PQQ-NAD(P)H system requires about 1 mol of O2 for the oxidation of 1 mol of NAD(P)H. The oxidation of NAD(P)H occurred at a pseudo-first-order rate with respect to NAD(P)H and was of zero order with respect to PQQ concentration in in the presence of O2: k0[PQQ] [NAD(P)H] = k1 [NAD(P)H], where k0[PQQ] = k1, in which [PQQ] represents the initial concentration of PQQ. k0 values for NADH and NADPH were 3.4.10(2) M-1.min-1 and 2.0.10(2) M-1.min-1, respectively, at 25 degrees C and at 258 microM O2 (initial concentration). The system produced O-2, probably by the interaction of PQQ.H and/or NAD(P).with O2, during the oxidation of NAD(P)H. PQQH2 and PQQ.H were easily oxidized to PQQ in the presence of O2, yielding H2O2.
在生理pH值且存在O₂的条件下，吡咯喹啉醌（PQQ）对NAD(P)H的氧化反应以非酶方式进行。PQQ-NAD(P)H体系氧化1摩尔NAD(P)H大约需要1摩尔O₂。在有O₂存在时，NAD(P)H的氧化反应对NAD(P)H呈假一级反应速率，对PQQ浓度呈零级反应：k₀[PQQ][NAD(P)H] = k₁[NAD(P)H]，其中k₀[PQQ] = k₁，[PQQ]表示PQQ的初始浓度。在25℃和258微摩尔O₂（初始浓度）条件下，NADH和NADPH的k₀值分别为3.4×10²M⁻¹·min⁻¹和2.0×10²M⁻¹·min⁻¹。在NAD(P)H氧化过程中，该体系可能通过PQQ·H和/或NAD(P)与O₂的相互作用产生超氧阴离子（O₂⁻）。在有O₂存在时，PQQH₂和PQQ·H很容易被氧化为PQQ，生成过氧化氢（H₂O₂）。
