Abstract
The steady state kinetics of phenazine methosulfate-catalyzed, photosystem I-driven photophosphorylation with spinach thylakoid membranes has been measured. The Km for ADP is 85 +/- 20 microM and the Km for phosphate is 0.58 +/- 0.11 mM. Adenosine-5'-O-(thiodiphosphate) (beta-ThioADP) is a competitive inhibitor with respect to ADP at high phosphate concentrations (Kis = 105 +/- 14 microM), but is a noncompetitive inhibitor with respect to phosphate (at all ADP concentrations) and ADP at low phosphate concentrations. Thiophosphate is a competitive inhibitor with respect to phosphate (Kis = 95 +/- 9 microM), but an uncompetitive inhibitor with respect to ADP. ADP also inhibits the rate of phosphorylation at high ADP to phosphate ratios. An ordered Bi Uni mechanism with ADP preceding the binding of phosphate is proposed to explain the kinetic data.
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.
