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Kinetic mechanism of AKT/PKB enzyme family

Xiaoling Zhang1, Shiwen Zhang, Harvey Yamane

  • 1Department of Oncology Research, Amgen Inc., Thousand Oaks, California 91320, USA. xzhang@amgen.com

The Journal of Biological Chemistry
|March 17, 2006
PubMed

Insights

This study reveals the AKT enzyme family follows a sequential kinetic mechanism, with ATP binding first. Understanding these AKT kinase mechanisms is crucial for cancer research and drug development.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • The AKT/PKB serine/threonine protein kinase is vital for cellular signal transduction.
  • Aberrant AKT activation contributes to cancer development through oncogenic pathways.

Purpose of the Study:

  • To characterize and compare the kinetic mechanisms of the three AKT isoforms (AKT1, AKT2, AKT3).
  • To elucidate the substrate binding and product release order for AKT enzymes.

Main Methods:

  • Initial velocity studies to determine kinetic mechanisms.
  • Product inhibition assays to analyze substrate addition order.
  • Steady-state kinetics with dead-end inhibitors for AKT1.

Main Results:

  • All AKT isoforms exhibit a sequential kinetic mechanism, forming an enzyme-substrate ternary complex.
  • Kinetic parameters (Km, kcat) differ among isoforms, with AKT2 having the highest Km for ATP and AKT3 the highest kcat.
  • Product inhibition patterns indicate an ordered mechanism where ATP binds before the peptide substrate.

Conclusions:

  • The AKT kinase family catalyzes reactions via an Ordered Bi Bi sequential mechanism.
  • ATP acts as an initiating substrate for AKT enzyme catalysis.
  • These findings offer insights into AKT enzyme regulation and potential therapeutic targeting in cancer.

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