Ganapathy V, Leibach F H
Biochim Biophys Acta. 1982 Oct 7;691(2):362-6. doi: 10.1016/0005-2736(82)90427-8.
L-Carnosine was shown to be transported into rabbit renal brush-border membrane vesicles by an Na+ -independent mechanism. The transport was competitively inhibited by glycyl-L-proline. Various di- and tripeptides inhibited L-carnosine transport, whereas free amino acids did not. Inhibition studies showed that blocking the free amino and carboxyl groups of the peptide reduced its affinity for the transport carrier. Under the conditions in which there was no detectable hydrolysis of L-carnosine in the medium, intravesicular contents showed a 30% hydrolysis of the peptide within the vesicles. Disruption of membrane vesicles with deoxycholate resulted in a 3-fold increase in L-carnosine hydrolyzing activity over untreated intact vesicles. Based on these observations, a model for peptide transport is proposed in which transport of the intact peptide across the membrane is followed by its partial or complete hydrolysis by a membrane peptidase whose active site is on the cytoplasmic side of the membrane.
已证明L-肌肽通过一种不依赖Na⁺的机制转运到兔肾刷状缘膜囊泡中。该转运受到甘氨酰-L-脯氨酸的竞争性抑制。各种二肽和三肽抑制L-肌肽的转运，而游离氨基酸则无此作用。抑制研究表明，封闭肽的游离氨基和羧基会降低其对转运载体的亲和力。在培养基中未检测到L-肌肽水解的条件下，囊泡内的物质显示囊泡内该肽有30%被水解。用脱氧胆酸盐破坏膜囊泡会导致L-肌肽水解活性比未处理的完整囊泡增加3倍。基于这些观察结果，提出了一种肽转运模型，即完整肽跨膜转运后，由膜肽酶对其进行部分或完全水解，该膜肽酶的活性位点位于膜的细胞质一侧。
