| abstract |
This specification discloses assay systems which detect the presence of, or measure or monitor the extent of, an enzyme-catalysed reaction on a substrate. The systems of the present invention can be used to detect or measure the enzyme or the substrate, depending upon circumstances. n The specification further discloses a method of assay of the type in which an electrode (1) poised at a suitable potential is contacted with a system comprising a first enzyme, (GO) a substrate (G) which undergoes a reaction catalysed by the said enzyme, and a mediator compound (F) which transfers charge to the electrode (1) from the first enzyme (GO) when it is catalytically active, whereby the current flowing in the electrode is a measure of the reaction taking place; in which at least one further enzyme (HK) and associated compound (ATP) is incorporated into the system, the further enzyme (HK) being productive of, or also being reactive with, the substrate (G) so as to affect its presence or level, but not being electrochemically linked by the mediator (F) to the electrode (1), whereby the consequent difference in electrode current flowing with, and in the absence of, the second enzyme (HK) and its associated compound is a measure of the extent of reaction of the further enzyme with its associated compound and thus permits the amount of one to be established if the amount of the other is known. n There are two main subdivisions of the present disclosure (i) in which the electrode is provided at its surface with the first enzyme and the mediator compound to constitute a sensor electrode and (ii) in which the further enzyme exerts a catalytic change on a specific further substrate to yield substrateforthe first enzyme. |