Kinetic Analysis of PRMT1 Reveals Multifactorial Processivity and a Sequential Ordered Mechanism

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• Arginine methylation is a key post-translational modification in eukaryotes.
• Debates persist regarding the processivity (processive vs. distributive) and substrate binding (random vs. sequential) mechanisms of arginine methyltransferases.
• Understanding these mechanisms is crucial for elucidating enzyme function and developing targeted inhibitors.

Purpose of the Study:

• To investigate the enzyme kinetics and mechanism of human protein arginine N-methyltransferase 1 (PRMT1).
• To determine whether PRMT1 operates via a processive or distributive mechanism and a random or sequential bisubstrate binding.
• To explore the implications of substrate sequence and potential inhibitors for PRMT1 activity.

Main Methods:

• Steady-state kinetic analysis of PRMT1.
• Enzyme kinetic assays using various peptide substrates, including those with Nη-hydroxyarginine.
• Kinetic modeling to determine the mechanism of action and processivity.

Main Results:

• PRMT1 enzyme kinetics were found to be substrate sequence-dependent.
• Peptides with Nη-hydroxyarginine exhibited substrate inhibition and altered K_M values, suggesting potential for inhibitor design.
• Enzyme processivity was influenced by both cofactor and enzyme concentrations, necessitating reassessment of previous conclusions.
• A sequential ordered Bi-Bi kinetic mechanism was elucidated for PRMT1.

Conclusions:

• PRMT1 follows a sequential ordered Bi-Bi kinetic mechanism.
• The study clarifies the mechanism of action and processivity of PRMT1.
• These findings may be applicable to other functionally and structurally conserved protein arginine methyltransferases (PRMTs).