All of the following enzymes are regulated by calcium or calmodulin, except: (A) Adenylate cyclase, (B) Glycogen synthase, (C) Guanylyl cyclase, (D) Hexokinase
Answer is D. Ca2+ is needed for the direct activation of enzymes such as lipase (pancreatic), ATPase and succinate dehydrogenase. Calmodulin mediated action of Ca2+: Calmodulin is a calcium-binding regulatory protein. Ca-calmodulin complex activates ceain enzymes e.g. adenylate cyclase, Ca2+ dependent protein kinases, glycogen synthase, glycerol-3-phosphate dehydrogenase ref DM Vasudevan 8th ed page 492 box 34.2