Pairoba C F, Colombo S L, Andreo C S
Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI, CONICET-Fund M. Lillo), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Argentina.
Biosci Biotechnol Biochem. 1996 May;60(5):779-83. doi: 10.1271/bbb.60.779.
The inhibitory effects of flavonoids on the activity of two photosynthetic enzymes such as phosphoenolpyruvate carboxylase (PEPCase) and NADP-dependent malic enzyme (NADP-ME) were evaluated. The glycosylation of hydroxyl groups on the flavonoids resulted in compounds that behaved as gradually weaker inhibitors with increased size of the substituent. Quercetin and baicalein showed a competitive inhibition pattern vs. NADP+ for NADP-ME, and a similar model for both flavonoids vs. phosphoenolpyruvate (PEP) was observed when tested on PEPCase. K(i) for NADP-ME inhibition at pH 7.0 were 0.83 microM and 1.54 microM for quercetin and baicalein, respectively. K(i) for PEPCase inhibition were 0.17 microM and 0.79 microM (quercetin and baicalein, respectively), indicating that these compounds are the most potent inhibitors described for this carboxylase. I50 values for these and other flavonoids were in the micromolar range. A tentative physiological role for the inhibitory effects observed on PEPCase is discussed.
评估了黄酮类化合物对两种光合酶，即磷酸烯醇式丙酮酸羧化酶（PEPCase）和依赖于NADP的苹果酸酶（NADP-ME）活性的抑制作用。黄酮类化合物上羟基的糖基化导致随着取代基尺寸增加，化合物作为抑制剂的作用逐渐减弱。槲皮素和黄芩苷对NADP-ME表现出与NADP +的竞争性抑制模式，并且在对PEPCase进行测试时，观察到两种黄酮类化合物对磷酸烯醇式丙酮酸（PEP）具有类似的模式。在pH 7.0时，槲皮素和黄芩苷对NADP-ME抑制的K（i）分别为0.83 microM和1.54 microM。对PEPCase抑制的K（i）分别为0.17 microM和0.79 microM（分别为槲皮素和黄芩苷），表明这些化合物是已报道的对该羧化酶最有效的抑制剂。这些以及其他黄酮类化合物的I50值在微摩尔范围内。讨论了观察到的对PEPCase抑制作用的初步生理作用。
