Recent studies have identified the proton-coupled folate transporter (PCFT) as the mechanism by which folates are absorbed across the apical brush-border membrane of the small intestine and across the basolateral membrane of the choroid plexus into the cerebrospinal fluid. Both processes are defective when there are loss-of-function mutations in this gene as occurs in the autosomal recessive disorder hereditary folate malabsorption. Because this transporter functions optimally at low pH, antifolates are being developed that are highly specific for PCFT in order to achieve selective delivery to malignant cells within the acidic environment of solid tumors. PCFT has a spectrum of affinities for folates and antifolates that narrows and increases at low pH. Residues have been identified that play a role in folate and proton binding, proton coupling, and oscillation of the carrier between its conformational states.

中文翻译：

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质子耦合叶酸转运蛋白：生理和药理作用。

最近的研究已经确定质子耦合叶酸转运蛋白 (PCFT) 作为叶酸被吸收穿过小肠的顶端刷状缘膜和穿过脉络丛的基底外侧膜进入脑脊液的机制。当该基因发生功能丧失突变时，这两个过程都有缺陷，如常染色体隐性遗传病遗传性叶酸吸收不良。由于这种转运蛋白在低 pH 值下发挥最佳功能，因此正在开发对 PCFT 具有高度特异性的抗叶酸剂，以便在实体瘤的酸性环境中选择性递送至恶性细胞。PCFT 对叶酸和抗叶酸的亲和性谱在低 pH 值下变窄和增加。已鉴定出在叶酸和质子结合、质子偶联、