Enzymatic Logic Gates with Noise-Reducing Sigmoid Response

Biochemical computing is an emerging field of unconventional computing that attempts to process information with biomolecules and biological objects using Boolean logic. In this work electrode-immobilized glucose-6-phosphate dehydrogenase enzyme catalyzed a reaction which carries out the Boolean AND logic gate. We report the first experimental realization of a sigmoid shape response in one of the gate inputs which is a desirable shape for biocomputing application as it allows reduction of the analog noise. A kinetic model is also developed and used to evaluate the extent to which the experimentally realized gate is close to optimal. Recently there has been significant interest in biochemical [1] information processing, including that based on enzyme reactions [2]. Enzymatic reactions have been shown to mimic digital logic gate functions [3] and elementary arithmetic operations [4] as well as “networked” in Boolean logic circuits [5]. Here we consider the AND logic function based on electrode-immobilized enzyme glucose-6-phosphate dehydrogenase (G6PDH). The biocatalytic reaction G6PDH G6P NAD NADH + + → + (1) has two inputs: glucose-6 phosphate (G6P) and cofactor nicotinamide adenine dinucleotide (NAD), and one output: the reduced cofactor (NADH); the other product ( ) in aqueous solution is 6-phosphogluconate. G6PDH is used in biosensors [6] for biomedical applications.