This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzyme regulation, Subject name: Biochemistry
[{'content': 'All of the following enzymes are regulated by calcium/calmodulin, EXCEPT \nSelect and explain. \nA. Hexokinase, B. Nitric oxide synthase, C. Pyruvate dehydrogenase, D. Phosphatidyl Inositol 3 kinase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Calmodulin is a calcium dependent small regulatory protein homologous to troponin C. It can bind to 4 calcium ions, binding of calcium leads to conformational change and fuher effects. Calmodulin can be found as a component of multisubunit proteins like phosphorylase kinase. Some enzymes regulated by calcium/calmodulin: Adenylyl cyclase Guanylyl cyclase Nitric oxide synthase Glutamate decarboxylase Phosphatidyl Inositol 3 kinase Myosin light chain kinase cAMP phosphodiesterase Pyruvate dehydrogenase Phospholipase A2 Glycogen phosphorylase kinase Hexokinase is a constitutively expressed enzyme. It is inhibited by its product glucose-6-phosphate.', 'role': 'assistant'}]