This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymology, Subject name: Biochemistry
Which of the following is a lyase 
Select and explain. 
A. Aldolase, B. Fumarase, C. Decarboxylase, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: 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.