Biotin transport in basolateral membrane vesicles of human intestine.
Biotin transport in basolateral membrane vesicles of human intestine.
复制标题
人肠基底外侧膜囊泡中的生物素转运。
DOI：
10.1016/0016-5085(88)90007-8
复制
发表时间：
1988
期刊：
影响因子：
29.4
通讯作者：
Nylander,W
中科院分区：
文献类型：
--
作者：
Said,HM;Redha,R;Nylander,W
生物素从肠上皮细胞排出过程的特征，即，使用人肠的富集的基底外侧膜囊泡制备物测定穿过基底外侧膜的转运。通过酶和功能标准确认了基底外侧膜囊泡用于转运研究的纯度和适用性。[~ 3 H]哇巴因结合研究确定了人基底外侧膜囊泡的取向，发现64%的囊泡是由内而外的，其余的是正面外的囊泡和膜片。渗透压研究表明，这些囊泡对生物素的摄取代表转运至囊泡内室，与膜表面的结合很少。生物素转运速率在约40 s内呈线性，但此后下降。生物素的转运是（a）Na+非依赖性的，（B）作为浓度的函数是饱和的，表观Km为1.1 μM，Vmax为0.9 pmol/mg蛋白· 15 s，（c）被结构类似物（脱硫生物素和生物素甲酯）和相关化合物（硫辛酸和硫辛酸酰胺）抑制，（d）通过诱导正囊内电位来刺激。这些研究首次证明了在人肠基底外侧膜中存在载体介导的生物素转运系统。
The characteristics of the exit process of biotin from the enterocyte, i.e., transport across the basolateral membrane, was determined using an enriched basolateral membrane vesicle preparation of human intestine. Purity and suitability of basolateral membrane vesicles for transport studies was confirmed by enzymatic and functional criteria. Orientation of human basolateral membrane vesicles was determined by [3H]ouabain binding studies and was found to be 64% inside-out vesicles and the rest right-side-out vesicles and membrane sheets. Osmolarity studies indicated that the uptake of biotin by these vesicles represents transport into the intravesicular compartment, with little binding to membrane surfaces. The rate of biotin transport was linear for ~40 s but decreased thereafter. Transport of biotin was (a) Na+-independent, (b) saturable as a function of concentration, with an apparentKMof 1.1 μM andVmaxof 0.9 pmol/mg protein · 15 s, (c) inhibited by structural analogues (desthiobiotin and biotin methyl ester) and related compounds (thioctic acid and thioctic amide), and (d) stimulated by inducing a positive intravesicular electrical potential. These studies are the first to demonstrate the existence of a carrier-mediated transport system for biotin in the basolateral membrane of human intestine.