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