Intestinal absorption of undegraded proteins in men: Presence of bromelain in plasma after oral intake
Intestinal absorption of undegraded proteins in men: Presence of bromelain in plasma after oral intake
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DOI：
10.1152/ajpgi.1997.273.1.g139
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发表时间：
1997-07-01
影响因子：
4.5
通讯作者：
Poppe, GE
中科院分区：
文献类型：
--
作者：
Castell, JV;Friedrich, G;Poppe, GE
人类成人的肠道上皮传统上被描述为对蛋白质不能渗透。然而，间接证据表明，在生理条件下，对未降解蛋白质的吸收可能会减少。以菠萝酶(一种从菠萝茎中提取的酶)作为模型蛋白，研究了19名健康男性的这种粘膜渗透程度。用免疫分析法检测该蛋白在血浆中的含量，并测定其口服后的蛋白降解活性。血浆半衰期估计为6~9h，口服多剂量(3g/d)后48h血药浓度高达5000pg/ml，从血药浓度曲线推算，菠萝酶在3~51h的平均血药浓度为10.8mg.用抗菠萝酶抗体免疫沉淀血浆样品，然后进行凝胶电泳和免疫检测，可以明确地证明血浆中存在未降解的菠萝酶。此外，该酶至少部分地保持了其生物活性。循环菠萝酶与α(2)-巨球蛋白和α(1)-抗糜蛋白酶有关。这项工作的结果证实了健康男性体内存在少量但显著的未降解蛋白质的肠道运输。
The human adult intestinal epithelium has traditionally been described as nonpermeable to proteins. However, indirect evidence suggests that reduced absorption of undegraded proteins might take place under physiological conditions. Using bromelain (an enzyme obtained from pineapple stems) as a model protein, we studied the extent of this mucosal permeation in 19 healthy men. The protein was detected in plasma by immunoassay and by its proteolytic activity after oral administration. The estimated plasma half-life was 6-9 h. After oral multidosing (3 g/day), plasma concentration reached as much as 5,000 pg/ml by 48 h. From the plasma concentration curve, it could be estimated that an average of 10.8 mu g of bromelain was present in plasma in the 3- to 51-h period. The presence of undegraded bromelain in plasma was shown unequivocally by immunoprecipitation of plasma samples with antibromelain antibodies, followed by gel electrophoresis and immunodetection. Moreover, the enzyme retained its biological activity, at least in part. Circulating bromelain was found associated with a(2)-macroglobulin and alpha(1)-antichymotrypsin. The results of this work confirm the existence of a small but significant intestinal transport of undegraded proteins in healthy men.