There are remarkably few papers in the literature on this topic [conductivity used to monitor enzyme catalysis, at least that I have been able to find that are relevant to the present work). However it is hardly a recent topic, since Henri used the method to measure gelatin hydrolysis by trypsin in 1903! Conductimetry has been widely applied in micro-biosensors, but I have excluded these (with an exception at the end) as they are 'High-Tech'. A recent literature search [07/04/2019] did not reveal any papers after the ones listed here , the latest being 2015. If you know of other publications that are relevant plase let me know. so I can include them.
For an excellent general text on enzyme assays I would like to refer you to the book of this title edited by Robert Eisenthal & Mike Danson
(see Google for online version)
This book contains a chapter written by my PhD supervisor Keith Brocklehurst
I also authored a book 'Molecular Enzymology' with Robert who was a very clever & original guy who devised, by lateral thinking, the Direct Linear Plot for kinetic analysis
Enzyme catalysed reactions measured by conductivity changes