Because enzymes usually require distinct pH conditions for maximum activity, an approach of spontaneous pH shift of solution was devised to derive multiple reactions in a sequence. The two enzymes selected, horseradish peroxidase (HRP) and beta-galactosidase (GAL), had dissimilar optimal pH levels, i.e., 5.1 and 7.0, respectively. In a solution, HRP initially reacted at a lower pH range and the GAL reaction was consecutively carried out at a higher range in the presence of a third enzyme, urease, which caused an increase in pH. Under optimal conditions, the multiple system provided comparable performances with those of single reactions.