Department of Biochemistry, Aichi Medical University, Nagakute, Aichi 480-1195, Japan.
Food Funct. 2012 Jun;3(6):674-8. doi: 10.1039/c2fo10245e.
Angiotensin I converting enzyme (ACE) was inhibited by the culture medium of Bacillus subtilis subsp. natto, which ferments boiled soy beans to natto, a Japanese traditional food. Subtilisin NAT (nattokinase) produced by B. subtilis also inhibited ACE, and the inhibition was markedly stimulated by heat treatment of subtilisin at 120 °C for 15 min. Inhibition of ACE by subtilisin was of a mixed type: the decrease in V(max) and the increase in K(m) value. SDS-polyacrylamide gel electrophoresis showed that heat treatment of subtilisin caused inactivation with fragmentation of the enzyme protein into small peptides. The inhibitory action of subtilisin was not due to an enzymatic action of protease, but may be ascribed to the potent ACE-inhibitory peptides such as LY and FY, amino acid sequences in subtilisin. HPLC-MS analysis of heat-inactivated subtilisin confirmed that LY and FY were liberated by fragmentation of the enzyme. Inhibition of ACE by subtilisin and its degradation peptides such as LY and FY may participate in the suppression of blood pressure by ingestion of natto.
纳豆枯草芽孢杆菌亚种发酵煮熟的大豆制成纳豆，纳豆枯草芽孢杆菌亚种发酵煮熟的大豆制成纳豆，其发酵液可抑制血管紧张素转化酶（ACE）。纳豆枯草芽孢杆菌亚种产生的枯草溶菌素 NAT（纳豆激酶）也可抑制 ACE，并且枯草溶菌素在 120°C 下热处理 15 分钟可显著增强其抑制作用。枯草溶菌素对 ACE 的抑制作用属于混合型：Vmax 值降低，K(m) 值升高。SDS-聚丙烯酰胺凝胶电泳显示，枯草溶菌素的热处理会导致酶蛋白失活并断裂成小肽。枯草溶菌素的抑制作用不是由于蛋白酶的酶促作用，而是可能归因于其强烈的 ACE 抑制肽，如 LY 和 FY，这些氨基酸序列存在于枯草溶菌素中。经热处理失活的枯草溶菌素的 HPLC-MS 分析证实，酶的断裂会释放出 LY 和 FY。枯草溶菌素及其降解肽，如 LY 和 FY，对 ACE 的抑制作用可能参与了纳豆摄入对血压的抑制。
