Measurement of Enzyme Activities and Optimization of Continuous and Discontinuous Assays.

The measurement of enzyme activities represents an important step towards the understanding of biological networks. Continuous or discontinuous assays can be used, as well as highly sensitive assays, depending on the abundance of the enzymes under study. To exemplify such methods, two protocols for phosphoenolpyruvate carboxylase activity (EC 4.1.1.31) in plant extracts are given. For this, an extraction protocol is also described. Then, an optimization protocol for enzyme assays using enzymatic, chemical, or biological standards is proposed. This protocol evaluates in one run the optimal extract dilution, the recovery of a standard, and the technical error in a given matrix. The interest of using biological standard in routine measurements is highlighted. © 2016 by John Wiley & Sons, Inc.