Linked enzyme assays
Numerous reactions do not include products or substrates which absorb light at a suitable wavelength. In this case it is frequently possible to assay the enzyme which catalyzes this reaction through linking or coupling it to a second enzyme reaction which does include a features absorbance modification. For instance, the action of the enzyme glucose oxidase, that is frequently used to measure the concentration of glucose in the blood of diabetic patients doesn’t result in a change in absorbance upon conversion of substrates to products which is shown in the figure. Moreover, the hydrogen peroxide produced in this reaction can be acted on through a second peroxidase, enzyme, that concurrently translates a colorless compound into a colored one (chromogen) whose absorbance can be simply measured.
![118_Linked enzyme assays.png](https://www.expertsmind.com/CMSImages/118_Linked%20enzyme%20assays.png)
If the activity of the first enzyme glucose oxidase is to be measured accurately the second enzyme peroxidase and its cosubstrates or coenzymes must be in excess so as not to be the rate-limiting step of the connected assay. This will ensure which the rate of production of the colored chromogen is proportional to