If the quantitatively determinable substance contained in the cells of the reagent is {HEAD ~ enzyme} , this reagent further contains a substrate which specifically interacts with {TAIL ~ the enzyme}  
If the quantitatively determinable substance contained in the cells of the reagent is { HEAD ~ enzyme } , this reagent further contains a substrate which specifically interacts with { TAIL ~ the enzyme }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH