Analytical Sciences

Promotion Effect by ε-Poly-L-lysine on the Enzymatic Reaction of Glucose Oxidase with Ferricyanide Ion as an Oxidant

Kohei UEMATSU, Misato YAMASAKI, Takao HIBI, and Hajime KATANO

Faculty of Biotechnology, Fukui Prefectural University, Eiheiji, Fukui 910-1195, Japan

An enzymatic reaction rate of glucose oxidase (GOD) using ferricyanide ion ([Fe(CN)₆]³⁻) as an oxidant significantly increased by the addition of ε-poly-L-lysine (ε-PL). The bimolecular rate constant between GOD and [Fe(CN)₆]³⁻ in the presence of ε-PL reached about 10000-fold relative to what it was measured without the ε-PL, and the Michaelis constant decreased. The reaction rate reached a maximum at around pH 6, where ε-PL and GOD possess highly positive and negative charges, respectively. The increment of the reaction rate by ε-PL can be attributed to the electrostatic association of the polycationic ε-PL with the negatively charged GOD to form a polyion complex soluble in the aqueous medium. The adduction of the cationic polymer may relieve the electrostatic repulsion between GOD and [Fe(CN)₆]³⁻, so that the electron transfer effectively occurs between them.

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