Past work on this topic & References
There are remarkably few papers on this topic [conductivity used to monitor enzyme catalysis] in the literature (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'.
For an excellent general text on enzyme assays I would like to refer you to the book of this title editedby Robert Eisenthal & Mike Danson
(see Google)
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
Urease: (this paper is in French)
Hanss, M. & Rey, A. (1971) Biochem et Biophysics Acta, 227, 630-638
Cholinesterase: (this paper is in French)
Hanss, M. & Rey, A. (1971) Biochem et Biophysics Acta, 227, 618-629
A wide range of enzymes:
Lawrence, A.J. & Moores, G.R. (1972) Eur. J. Biochem. 24, 538-546