Calmodulin activates NAD kinase of sea urchin eggs: an early event of fertilization.
NAD kinase, one of the first enzymes activated after fertilization of sea urchin eggs, is regulated by Ca2+ and calmodulin in vitro. The evidence is the requirement for low amounts of Ca2+ (Kd for Ca2+ of 4 x 10(-7) M) and the dissociation of a heat-stable activator from the enzyme which is similar to calmodulin on the basis of radioimmunoassay, activation of bovine brain phosphodiesterase and coelectrophoresis of a major protein of the activator fraction with bovine calmodulin. Also, the calcium stimulation of the enzyme is prevented by trifluoperazine, an inhibitor of calmodulin-associated reactions. In vivo studies show that the enzyme is activated by artificial parthenogenesis regimes that increase cytosolic Ca2+, but not by ammonia activation which only partially activates eggs and bypasses the Ca2+-rise step. These in vitro and in vivo studies indicate that calmodulin is part of the linkage between the rise in Ca2+ at fertilization and the turning on of egg metabolism.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology*; D004789:Enzyme Activation; D005260:Female; D005306:Fertilization; D009243:NAD / Q000378:metabolism; D010063:Ovum / Q000201:enzymology*; D010770:Phosphotransferases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor); D012617:Sea Urchins
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D009243:NAD; D010770:Phosphotransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; D002118:Calcium