This hand book is excellent dictionary of instant notes on introduction, history, structure, mechanism, specificity, catalysis, allosteric modulation, coenzymes, cofactors, thermodynamics, kinetics, types of inhibitions (competitive inhibition, uncompetitve inhibition, non-competitive inhibition and mixed inhibition), use of inhibitors, biological functions, control of activity, role of enzymes in pathogenesis, nomenclature & classifications ans industrial application of enzymes along with the needful and important references. It also includes the instant and brief key notes on mechanism of catalysis including the transition state stabilization, dynamics and function performed by the enzymes. Dedicated to All Mighty and my dear parents, my father , Late Mr. Ram Kumar Sharma and my mother, Mrs. Sushila Sharma.