Effect of exogenous calmodulin and ATP on the activity of ethylene forming enzyme obtained from tomatoes and green pea pods

Ethylene forming enzymes (EFE) from both peas and tomatoes were prepared. EFE from both sources were inhibited by adenosine triphosphate (ATP). Exogeneous calmodulin had no effect on EYE activity either in the presence or absence of ATP. The presence of gramicidin in pea microsomal membrane EFE did not affect EFE activity in the presence of ATP. This suggests that ATP is inhibiting EYE activity through phosphorylation and not through transmembrane proton flux. However, inhibition of EFE activity by ATP was partially reversed by 60 μM N-6(aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) and 15 μM trifluoperazine (TFP) but not by 60 μM N-6(aminohexyl)-1-naphthalenesulphonamide (W5), which suggests that the ATP inhibitory affect on EFE is probably controlled by calmodulin.