The results of the study presented here provided greater understanding for previous chemical modification experiments that had been carried out with creatine kinase. These reactions are shown in Figure 15.3. Some investigators modified the Cys 278 with iodoacetamide and found that the enzyme activity was abolished as a result. They concluded that the Cys 278 residue was absolutely essential for enzymatic activity. But other investigators modified the Cys 278 with iodoacetate and found that activity was decreased but not abolished, leading them to conclude that the Cys 278 was not essential. Taking these results together with the results of the current study, can you suggest an explanation that will clear up the confusion