Abstract
A true ecto-apyrase (ATP diphosphohydrolase, EC 3.6.1.5) enzyme was found in the synaptosomal fraction from the electric organ of the electric ray Torpedo marmorata. The activity could not be attributed to the combined action of different enzymes. The pH requirement and calcium dependence were the same for hydrolysis of both substrates ADP and ATP. The enzyme had an apparent K m value of 117 μM for ATP and of 123 μM for ADP. The involvement of nonspecific phosphatases in the hydrolysis of both substrates was excluded. The enzyme hydrolyses almost equally well different nucleoside di- and triphosphates. ATP and ADP hydrolysis was not inhibited by seven ATPase inhibitors i.e., sodium azide, dinitrophenol, ruthenium red, oligomycin, ouabain, sodium orthovanadate and lanthanum.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
