Abstract
CTP synthetase (EC 6.3.4.2, UTP:ammonia ligase (ADP-forming)) is an allosterically regulated enzyme in the yeast Saccharomyces cerevisiae. In this work we examined the regulation of CTP synthetase activity by S. cerevisiae protein kinase C (Pkc1p) phosphorylation. The results of labeling experiments with S. cerevisiae mutants expressing different levels of the PKC1 gene indicated that phosphorylation of CTP synthetase was mediated by Pkc1p in vivo. In vitro, Pkc1p phosphorylated purified CTP synthetase on serine and threonine residues, which resulted in the activation (3-fold) of enzyme activity. The mechanism of this activation involved an increase in the apparent Vmax of the reaction and an increase in the enzyme's affinity for ATP. In vitro phosphorylated CTP synthetase also exhibited a decrease in its positive cooperative kinetic behavior with respect to UTP and ATP. Phosphorylation of CTP synthetase did not have a significant effect on the kinetic properties of the enzyme with respect to glutamine and GTP. Phosphorylation of CTP synthetase resulted in a decrease in the enzyme's sensitivity to product inhibition by CTP. Phosphorylation did not affect the mechanism by which CTP inhibits CTP synthetase activity.
Published Version (
Free)
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.
