This paper examines the solution kinetics of bovine intestinal and liver alkaline phosphatase (ALP) isozymes. 4-Methylumbelliferyl phosphate is used as the substrate to study the differential kinetic behavior of ALP isozymes in the presence of guanidinium hydrochloride, a denaturant. The recursive Kalman filter algorithm for parameter estimation is used for analysis of the resulting kinetic data. A two-component first-order kinetic model with a zero-order component is used to successfully quantify intestinal and liver isozymes in synthetic mixtures. This work serves as a basis for the development of an electrophoresis separation method for ALP isozyme quantification with differential kinetic detection.