Trade-off between carbohydrates and metal ions regulates the chemotactic directionality of alkaline phosphatase

Abstract

Herein we report the chemotactic behaviour of alkaline phosphatase (ALP) in the gradients of carbohydrates (glucose, fructose and sucrose) and metal ions, including cofactors (Zn²⁺ and Mg²⁺), under microfluidic conditions. We found that ALP migrates marginally away from the carbohydrate gradient, whereas for divalent metal ions, the direction is opposite and more prominent. This differential phoresis is due to the Hofmeister effect driven change in the ALP surface zeta potential and osmotic pressure imbalance. Gaining control over the chemotactic extent and direction of an enzyme in response to purely non-catalytic conditions will have potential application in designing environment-responsive nanomachines.