Polymerization Degree of Oligomethionine to Determine Its Bioavailability When Added to a Low-protein Diets
作者:Takanori Kasai、Tomoyuki Tanaka、Shuhachi Kiriyama
DOI:10.1271/bbb.60.828
日期:1996.1
Oligo-L-methionine ethylester (OMOEt) prepared by the papain-catalyzed oligomerization of L-methionine ethylester (MetOEt) is a mixture of pentamer to dodecamer and has nearly the same supplementary effect as free methionine (Met) for the growth of rats when added to a low casein diet, but its supplementary effect to a low-soy protein isolate (SPI) diet is not consistent and depends on the degree of polymerization. Rats were fed for 2wk with an 8% casein or 10% SPI diet supplemented with 0.3% L-Met, each chemically synthesized MetnOEt with a polymerization degree (n) of 6, 7, 8, or 9, or with OMOEt prepared by papain-catalyzed polymerization of MetOEt. Met6OEt, Met7OEt, and Met8OEt had nearly the same supplementary effect on the growth of rats, as did free Met, both with the 8% casein and 10% SPI diets. The supplementary effect of Met9OEt was not significantly lower than that of Met when added to the 8% casein diet, but was significantly lower when added to the 10% SPI diet. The digestibility of Met9OEt supplemented to the 8% casein and 10% SPI diets was 50.5% and 35.6%, respectively. It appears likely that there is a gap in the bioavailability of oligomethionine between the octamer and nonamer when added to a low-protein diet, probably due to the rigidity of the structure increasing with the polymerization degree by α-helix formation. Although the differences in absorption rate of Met from OMOEt for a short time after feeding has been related to the different effects of supplemented OMOEt, the absorption rate of OMOEt for 30 min after feeding was not considered to be the main cause of the differential effects of OMOEt in this experiment.
由木瓜蛋白酶催化 L-蛋氨酸乙酯(MetOEt)的低聚聚合反应制备的低聚 L-蛋氨酸乙酯(OMOEt)是一种五聚体到十二聚体的混合物,添加到低酪蛋白日粮中对大鼠生长的补充作用与游离蛋氨酸(Met)几乎相同,但添加到低大豆分离蛋白(SPI)日粮中的补充作用并不一致,而且取决于聚合度。用 8%的酪蛋白或 10%的 SPI 日粮喂养大鼠 2 周,并在日粮中添加 0.3% 的 L-Met、聚合度(n)为 6、7、8 或 9 的化学合成 MetnOEt 或通过木瓜蛋白酶催化聚合 MetOEt 制备的 OMOEt。与游离 Met 相比,Met6OEt、Met7OEt 和 Met8OEt 对大鼠生长的辅助作用几乎相同,均适用于 8% 酪蛋白和 10% SPI 日粮。添加到 8%酪蛋白日粮中时,Met9OEt 的补充效果并不明显低于 Met,但添加到 10%SPI日粮中时,Met9OEt 的补充效果明显低于 Met。在 8%酪蛋白日粮和 10%SPI日粮中添加 Met9OEt 的消化率分别为 50.5% 和 35.6%。在低蛋白日粮中添加低聚蛋氨酸时,八聚体和非八聚体之间的生物利用率可能存在差距,这可能是由于α-螺旋形成后,结构的刚性随着聚合度的增加而增加。尽管饲喂后短时间内 OMOEt 对 Met 的吸收率差异与添加 OMOEt 的不同效果有关,但饲喂后 30 分钟内 OMOEt 的吸收率并不是本实验中 OMOEt 不同效果的主要原因。