Why are enzymes always proteins?

Its a misconception that all enzymes are protein. There are examples where an enzymatic reaction is catalyzed by a bio molecule which is not protein. An example of this is the Ribozyme,an RNA molecule which is capable of catalyzing a reaction. read more

”. As others have pointed out in their answers, RNA can act as proteins as well. One of the reasons that most enzymes are proteins could be because of the structural organization of proteins. read more

- The ability of proteins to undergo shape changes and reversibly so, make them most suited to function as enzymes among other things. - Other biological macromlecules like sugars and fats are less suited for such a function. Some RNA molecules serve as enzymes too . And for the same reason,too. read more

Unlike fibrous proteins globular proteins are water soluble and they can form colloidal natures in aqueous systems. A large volume of the human body is composed of water. Most reactions that occur in the human system occur within this aqueous medium and enzymes that catalyse this reaction also have to be able to interact in the medium. read more