School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China.
School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China; School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Food Res Int. 2018 Mar;105:556-562. doi: 10.1016/j.foodres.2017.11.037. Epub 2017 Nov 21.
This study systematically explored the effect of HEPES, Tris and sodium phosphate (PB) buffers on the xanthine oxidase (XO) inhibitory activity of tuna protein hydrolysate (TPH, containing over 90% of constituents with molecular weight below 5kDa). The greatest XO inhibition by TPH was observed in HEPES buffer. The optimal HEPES concentration was 100mmol/L. Tryptophan fluorescence and circular dichroism measurements revealed the comparable stability of XO and TPH in the three buffers. The buffers did not alter the majority of XO or TPH structure but induced slight modifications to specific domains (e.g. Trp residues on α-helices) and certain rearrangements (e.g. XO unfolding or refolding). HEPES buffer exerted stronger interactions with XO or TPH, causing a lower α-helical content in XO and consequently a lower XO catalytic activity but greater XO inhibition, compared to Tris and PB buffers.
本研究系统地探讨了 HEPES、Tris 和磷酸钠 (PB) 缓冲液对金枪鱼蛋白水解物 (TPH，其 90%以上的成分分子量低于 5kDa) 的黄嘌呤氧化酶 (XO) 抑制活性的影响。TPH 对 XO 的最大抑制作用出现在 HEPES 缓冲液中。最佳 HEPES 浓度为 100mmol/L。色氨酸荧光和圆二色性测量表明，在三种缓冲液中，XO 和 TPH 的稳定性相当。缓冲液并未改变 XO 或 TPH 的大部分结构，但诱导了特定结构域的轻微变化（例如，α-螺旋上的色氨酸残基）和某些重排（例如，XO 展开或折叠）。HEPES 缓冲液与 XO 或 TPH 相互作用更强，导致 XO 的α-螺旋含量降低，从而降低 XO 的催化活性，但对 XO 的抑制作用更强，与 Tris 和 PB 缓冲液相比。
