Lactate dehydrogenase, single molecule

Enzyme catalyzed reactions have also been studied at the single molecule level. Earlier work involved measurement of beta-galactosidase activity in droplets after a 10-15 h incubation. In a recent study, detection of fluorescent product generated by individual molecules of lactate dehydrogenase after a 1 hr incubation has been achieved using capillary electrophoresis . The activity of individual molecules were reproducible but activity of different molecules showed a 5-fold range. The differences in activity were suggested to reflect differences in conformation. 

Single turnover experiments can also be used to test whether the sites of oligomeric enzymes are kinetically identical. For instance, lactate dehydrogenase has four active sites per molecule. The following parallel experiments were carried out... 

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