A convenient test for lipase activity in aqueous-based solutions

We proposed a convenient and accurate method for the measurement of lipase activity in a uniform aqueous-based substrate solution. In this work, lipase from Candida rugosa was used as the model lipase to test its catalytic ability toward p-nitrophenyl palmitate (p-NPP), which was suspended in a mixture of p-NPP ethanol solution and buffer. An ultraviolet-visible spectrophotometer was used to efficiently measure the liberated p-nitrophenol without extraction or centrifugation. Several factors that affected lipase activity were investigated, such as the ratio of p-NPP ethanol solution to buffer, the concentrations of p-NPP and lipase, as well as the temperature, reaction time, pH and agitation rate. Additionally, enzyme catalytic parameters such as K-m, V-m and activation energy were also assessed. We determined the optimal conditions for lipase in this homogeneous system and demonstrated lipase's catalytic performance in this condition followed Michealis-Menten kinetics. (C) 2015 Elsevier Inc. All rights reserved.