Controlled initiation of biochemical events and in particular of protein activity is a powerful tool in biochemical research. Specifically, optical trigger signals are an attractive approach for remote control of enzyme activity. We present a method for generating optical control of enzyme activity applicable to a widespread range of enzymes. The approach is based on short laser pulses as optical “switches” introducing an instantaneous change of the pH-value for activation of protein function. The pH-jump is induced by proton release from 2-nitrobenzaldehyde. Reaction conditions were chosen to yield a pH-jump of almost 3 units on switching from inactive to active conditions for the enzyme. In this experimental setup, irradiation can be realized without any loss of enzyme activity. Following this change in pH-value, a controlled activation of hydrolytic activity of acid phosphatase is successfully demonstrated. This application provides a general method for photocontrol of enzymatic function for proteins having a significant pH-profile. The kinetic data for the substrate 6-chloro-8-fluoro-4-methylumbelliferone phosphate are determined.