Substrate trafficking and dioxygen activation in bacterial multicomponent monooxygenases.

Area of Science:

• Biochemistry and enzymology
• Protein-protein interactions
• Catalysis

Background:

• Bacterial multicomponent monooxygenases feature non-heme carboxylate-bridged diiron centers crucial for catalysis.
• These enzymes process electrons, protons, dioxygen, and hydrocarbons, with selective hydrocarbon oxidation being a key function.
• Understanding substrate transport mediated by protein-protein interactions to the diiron center is a significant challenge.

Purpose of the Study:

• To summarize current knowledge on substrate transport and processing by diiron centers in bacterial monooxygenases.
• To highlight findings from methane monooxygenase, toluene/o-xylene monooxygenase, and phenol hydroxylase systems.
• To discuss the role of the protein framework in tuning diiron center reactivity.

Main Methods:

• Review of existing literature and research findings.
• Focus on experimental data from methane monooxygenase (MMO).
• Analysis of recent results from Pseudomonas sporium OX1 systems (toluene/o-xylene monooxygenase and phenol hydroxylase).

Main Results:

• Detailed examination of substrate processing (electrons, protons, dioxygen, hydrocarbons) at diiron centers.
• Observation of a distinct diiron(III) oxygenated intermediate in Pseudomonas sporium OX1 systems with unique Mössbauer parameters.
• Evidence suggesting significant complexity in how protein frameworks tune diiron center reactivity.

Conclusions:

• Protein-protein interactions play a critical role in mediating substrate delivery for selective hydrocarbon oxidation.
• The protein framework's ability to modulate the diiron center's reactivity is more intricate than previously understood.
• Comparative studies across different hydroxylase systems reveal nuanced mechanisms of enzymatic catalysis.