CSIRO Preventative Health Flagship, CSIRO Food and Nutritional Sciences, 671 Sneydes Road, Private Bag 16, Werribee, Victoria 3030, Australia.
Food Funct. 2011 Jun;2(6):310-9. doi: 10.1039/c1fo10023h. Epub 2011 May 26.
The focus of this study was to investigate Angiotensin Converting Enzyme (ACE) inhibiting activity across 34 teas (Camellia sinensis) produced by 5 different processing methods including green (GT), oolong (OT), white (WT), black (BT) and dark (DT) teas. In vitro ACE inhibitory activity was affected by the tea processing method with IC(50) values for ACE inhibition: green < oolong < white < black < dark teas. Substrate-dependence of the reaction kinetics was studied for GT and BT polyphenolic size fractions either < or > 3 kDa and also Green Tea Polyphenolic Isolate (GTPI), and revealed that enzyme velocity curves fitted allosteric, not Michaelis-Menten, relationships. Inhibition was weakly dependent on substrate concentration for GT fraction >3 kDa and independent of substrate concentration for all other GT and BT size fractions and GTPI. Furthermore, evidence for direct inactivation of ACE by GTPI was demonstrated. Overall, the results suggest that tea polyphenolics exert a mixed mode of in vitro inhibition of ACE, mostly of a kinetically uncompetitive type. The results are discussed in the context of in vivo and epidemiological evidence for regulation of blood pressure by tea consumption.
本研究的重点是研究 34 种不同加工方法（包括绿茶（GT）、乌龙茶（OT）、白茶（WT）、黑茶（BT）和红茶（DT））生产的 34 种茶（茶树）的血管紧张素转换酶（ACE）抑制活性。体外 ACE 抑制活性受茶加工方法的影响，ACE 抑制的 IC50 值为：绿茶<乌龙茶<白茶<黑茶<红茶。对 GT 和 BT 多酚大小分级（<3 kDa 和>3 kDa）以及绿茶多酚分离物（GTPI）进行了反应动力学的底物依赖性研究，结果表明酶速度曲线符合变构关系，而不是米氏关系。GT 分级>3 kDa 的抑制对底物浓度的依赖性较弱，而其他 GT 和 BT 分级以及 GTPI 的抑制对底物浓度不依赖。此外，还证明了 GTPI 对 ACE 的直接失活作用。总的来说，研究结果表明，茶多酚对 ACE 的体外抑制作用具有混合模式，主要是动力学非竞争性类型。结果在体内和流行病学证据的背景下讨论了茶对血压的调节作用。
