Abstract
1. 1.|The influence of the free Mg 2+ concentration on the kinetic parameters of M 2-type pyruvate kinase (ATP; pyruvate phosphotransferase, EC 2.7.1.40) from rat liver, isolated in the presence of the physiological free Mg 2+ concentration, is investigated. 2. 2.|At 1 mM Mg free 2+ and pH 7.5 the affinity of the enzyme for the substrate phosphoenolpyruvate is decreased as compared to 10 mM Mg free 2+, whereas the affinity for the second substrate ADP does not change. The decrease in affinity for phosphoenolpyruvate at low free Mg 2+ concentrations appears to be the consequence of the presence of a low affinity form of the enzyme. 3. 3.|It is shown that the ATP inhibition is mainly due to Mg 2+ binding and that it is probably not of physiological importance. 4. 4.|The enzyme possesses a high affinity for Fru-1,6- P 2 (half maximal activation at 1 μM) which is decreased by the addition of alanine. The affinity of the enzyme for Fru-1,6- P 2 at 0.1 mM phosphoenolpyruvate is not influenced by the free Mg 2+ concentration. In the presence of alanine the affinity for Fru-1,6- P 2 is increased by increasing the phosphoenolpyruvate concentration. 5. 5.|It is concluded that at physiological concentrations of alanine, Mg 2+, ADP and phosphoenolpyruvate the M 2-type pyruvate kinase activity is mainly dependent upon the Fru-1,6- P 2 concentration.
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.
