Abstract
Phosphorylase kinase (ATP:phosphorylase phosphotransferase, EC 2.7.1.38), the enzyme which regulates glycogen breakdown by converting α-glucan phosphorylase (α-1,4-glucan:orthophosphate glucosyltransferase, EC 2.4.1.1) into its active form, requires ATP and divalent metal ions for its activity. We have shown that: 1. 1.MgATP 2−2 chelate is the substrate for the reaction with an apparent K m of 0.07 mM ± 0.02 (S.D.). 2. 2.Free Mg 2+ in mM concentration is also required for activity. The apparent K a for free Mg 2+ is 0.6 mM ± 0.2 (S.D.). 3. 3.Free ATP 4− is not inhibitory. 4. 4.Mn and Ca at mM concentrations are inhibitors of the enzyme even though μM concentrations of Ca are required for activity 1,2. With both metals the inhibition is not competitive with respect to MgATP 2− and Mg 2+. Mn as well as Al, Ba and Co, in the absence of Mg, will allow the phosphorylase kinase reaction to proceed but only at approx. 5% of the rate observed in the presence of Mg.
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.
