ALBUMIN-BINDING OF INSULINS ACYLATED WITH FATTY-ACIDS - CHARACTERIZATION OF THE LIGAND PROTEIN-INTERACTION AND CORRELATION BETWEEN BINDING-AFFINITY AND TIMING OF THE INSULIN EFFECT IN-VIVO

Albumin is a multifunctional transport protein that binds a wide varie ty of endogenous substances and drugs. Insulins with affinity for albu min were engineered by acylation of the epsilon-amino group of Lys(B29 ) With saturated fatty acids containing 10-16 carbon atoms. The associ ation constants for binding of the fatty acid acylated insulins to hum an albumin are in the order of 10(4)-10(5) M(-1). The binding apparent ly involves both non-polar and ionic interactions with the protein. Th e acylated insulins bind at the long-chain fatty acid binding sites, b ut the binding affinity is lower than that of the free fatty acids and depends to a relatively small degree on the number of carbon atoms in the fatty acid chain. Differences in affinity of the acylated insulin s for albumin are reflected in the relative timing of the blood-glucos e-lowering effect after subcutaneous injection into rabbits. The acyla ted insulins provide a breakthrough in the search for soluble, prolong ed-action insulin preparations for basal delivery of the hormone to th e diabetic patient. We conclude that the biochemical concept of albumi n binding can be applied to protract the effect of insulin, and sugges t that derivatization with albumin-binding ligands could be generally applicable to prolong the action profile of peptide drugs.