Which of the following is a lyase

All of the above i.e. Fumarase, Aldolase, Decarboxylase are Lyases. Lyases are enzymes which can either break a bond or make a bond but they do not require water or ATP. The EC No. is 4. Fumarase is a Lyase (also known as Hydratase enzyme which can add or remove water but bond is not broken). Aldolase A & B both are Lyases. Simple Decarboxylases are Lyases. EXTRA EDGE: The other examples of Lyases are: Synthase - Link two molecules without involvement of ATP. Desulfhydrase - Remove H2S from substrate. Enzyme of Oxidative decarboxylation is a Dehydrogenase, so belongs to EC No.= 1 as compared to simple decarboxylases which are Lyases.