Plasma carrier proteins

Plasma carrier proteins are a heterogeneous group of soluble proteins in the blood that facilitate the transport of various endogenous and exogenous molecules, including hormones, lipids, vitamins, metal ions, and drugs (StatPearls, 2023). The most prominent member is human serum albumin, which provides significant oncotic pressure and possesses multiple binding sites for acidic and neutral drugs, serving as a primary reservoir in the circulation (UniProt P02768). Other specialized carriers include sex hormone-binding globulin (SHBG), transthyretin, and transferrin, which regulate the bioavailability of specific ligands by sequestering them and controlling the ratio of bound to free (biologically active) molecules (PubMed, 2021). These proteins play a critical role in pharmacokinetics, as only the unbound fraction of a drug is typically available to cross membranes and reach its therapeutic target (NCBI, 2023). Alterations in the concentration or binding affinity of these proteins, often seen in hepatic or renal impairment, can lead to significant changes in drug efficacy and toxicity (StatPearls, 2023). Furthermore, some carrier proteins like transthyretin are direct therapeutic targets for stabilizing ligands to prevent protein misfolding diseases such as amyloidosis (NIH, 2022).

Other names

Serum transport proteinsBlood carrier proteinsCirculating binding proteinsPlasma transport proteins

Reversible non-covalent binding to ligands to facilitate systemic transport, protect ligands from premature metabolism, and modulate the free drug fraction available for tissue distribution.