This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the  following enzyme is not regulated by calcium or calmodulin? 
Select and explain. 
A. Adenylate cyclase, B. Glycogen synthase, C. Guanylyl cyclase, D. Hexokinase
D: Hexokinase
Answer: D: Hexokinase 
Explanation: Calmodulin  mediated  action  of  Ca2+ : Calmodulin (mol.  wt.  17,000) is  a  calcium binding  regulatory  protein.  Ca-calmodulin complex  activates  certain  enzymes 
e.g. adenylate cyclase,  Ca2+  dependent  protein kinases.
Ref: Satyanrayana, Ed 3, page no 405