Comparison kinetics of Escherichia coli β‐galactosidase using a Microplate reader and a Genosys 5 spectrophotometer

Based on the rationale that students perceive more relationship between exercises using different techniques or instruments and the concepts built upon foundational material in undergraduate biochemistry courses, we have developed a module on E. coli β‐galactosidase enzyme, in our comprehensive one‐semester laboratory course. We have used the E. coli ML308 (ATCC 15224) strain which is constitutive for β‐galactosidase expression, the pET‐15b plasmid (Novagen) that contains the β‐galactosidase coding sequence inserted into pET15b with a 6X His‐tag on the N terminus and also the commercially available β‐galactosidase from Sigma. Purified enzyme preparations of all of the above three sources were tested for their kinetics using both a relatively less expensive microplate reader (Awareness Technology) and a Spectronic Genosys 5 spectrophotometer (Thermo Fisher). In general, the results indicated that though the trends were the same, the plate reader gave consistently higher values for all the parameters that were studied. Data obtained from the β‐galactosidase kinetic studies using both instruments, will be presented.