Kinetic analysis of biotinylation of specific residues of peptides by high-performance liquid chromatography.

A procedure employing C18 reversed-phase high-performance liquid chromatography (HPLC) is described for evaluating the kinetics of biotinylation of specific residues of peptides after reaction with N-hydroxysuccinimide esters of biotin. Utilizing this HPLC method, we determined the observed pseudo-first-order reaction rate constant (k'1) of biotinylation of lysyl residues in two model peptides, [biotinyl-Ser108]ProA-egg laying hormone (108-121) and pGlu-Lys-Trp-Ala-Pro, to be 1.22.10(-2)s-1 and 1.08.10(-2)s-1, respectively, in 0.05 M sodium phosphate buffer, pH 8.2, at 25 degrees C. The respective reaction half-lives of the two peptides were 57 s and 64 s. In addition, HPLC analytical methods were established for determining the time-course of hydrolysis of biotinylating reagents at acidic and alkaline pH and for evaluating biotin reagent homogeneity.