Deciphering Binding Site Conformational Variability of Substrate Promiscuous and Specialist Enzymes

Area of Science:

• Biochemistry
• Enzymology
• Structural Biology

Background:

• Substrate promiscuity allows enzymes to catalyze reactions with non-native substrates, expanding their functional repertoire and aiding evolutionary adaptation or enzyme design.
• The molecular underpinnings of substrate promiscuity are not fully understood, but active site conformational flexibility is increasingly recognized as a key factor.
• It is hypothesized that enzymes accommodate alternate substrates through pre-existing conformational states within their active sites.

Purpose of the Study:

• To investigate the role of active site conformational flexibility in substrate promiscuity.
• To compare the conformational dynamics of substrate-binding competent states in promiscuous versus specialist enzymes.

Main Methods:

• Employed long-time explicit water molecular dynamics simulations to analyze enzyme conformations.
• Visually assessed the variability of alternate enzyme conformations.
• Quantitatively evaluated substrate-binding competent conformations using a native functionality score.

Main Results:

• Identified multiple substrate-binding competent conformers in both promiscuous and specialist enzymes.
• Observed that restrictive conformers were also present in both enzyme types.
• Demonstrated that conformational dynamics are crucial for substrate binding in both enzyme categories, though to different degrees.

Conclusions:

• Conformational dynamics of enzyme active sites play a significant role in substrate binding.
• Both promiscuous and specialist enzymes exhibit conformational flexibility that allows for the binding of various substrates.
• The extent of conformational flexibility influences the degree of substrate promiscuity observed in enzymes.