The structural basis for specificity in lipoxygenase catalysis

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Lipoxygenases (LOX) catalyze the precise oxygenation of polyunsaturated fatty acids.
• Understanding LOX catalysis is challenging due to the transient nature of substrate binding and reaction intermediates.
• Structural insights are crucial for elucidating the mechanism of regioselective and stereoselective oxygenation.

Purpose of the Study:

• To review and consolidate current structural data on lipoxygenase (LOX) enzymes.
• To explain the structural basis for substrate binding, orientation, and regioselective/stereoselective oxygenation.
• To highlight the roles of different LOX domains in catalysis and product specificity.

Main Methods:

• Analysis of available crystal structures of lipoxygenases, including those with inhibitors, surrogate substrates, and arachidonic acid.
• Focus on the U-shaped fatty acid binding channel and the catalytic domain.
• Examination of the N-terminal β-barrel (C2-like/PLAT domain) and its functions.

Main Results:

• LOX enzymes utilize a U-shaped channel for fatty acid binding.
• Distinct amino acids dictate substrate orientation and positioning of the pentadiene for hydrogen abstraction.
• The N-terminal domain influences substrate acquisition and calcium sensitivity, while the catalytic domain governs oxygenation specificity.
• Conserved catalytic machinery underlies differing product specificities among LOX enzymes.

Conclusions:

• Structural data reveals how LOX enzymes achieve precise oxygenation of fatty acids.
• Enzyme structure dictates the regioselective and stereoselective formation of hydroperoxide products.
• Differences in product specificity arise from variations in amino acid residues within conserved catalytic domains.