Enzyme - based sensors are more specific than cell based sensors. They have faster responds due to shorter diffusion paths. They are expensive to produce due to the problem of isolating the enzyme. Glucose biosensor is mostly used biosensor. An enzyme biosensor is an analytical device that combines an enzyme with a transducer in order to produce a signal proportional to target analyte concentration. Optimal enzyme activity is essential for maintenance of physiological homeostasis. Both non-genetic and genetic disruptions can excessively activate or silence intrinsic enzyme activities, with pathological outcomes. The pharmacological agents are activators and inhibitors of enzymes. It is essential in the development of drugs as enzyme activators and inhibitors that enzyme activities be accurately measured under physiological and pathological conditions. Different biochemical assays have been developed for this, some of which are based on nanostructured materials. There has been an increased interest in the use of electrochemical sensors in clinical diagnostics. The coupling of enzymes with electrochemical sensors permits the simple determination of metabolites, therapeutic drugs, antigens, and antibodies.