Molybdenum-cofactor-containing enzymes: structure and mechanism

Area of Science:

• Biochemistry
• Enzymology
• Metalloprotein chemistry

Background:

• Molybdenum-containing enzymes are vital catalysts in nitrogen, sulfur, and carbon metabolic cycles.
• Molybdenum is incorporated into proteins via the molybdenum cofactor, featuring a mononuclear molybdenum atom linked to molybdopterin.
• Tungsten can substitute for molybdenum in some microorganisms.

Purpose of the Study:

• To review the structural and mechanistic aspects of molybdenum-cofactor-containing enzymes.
• To discuss the active site structures and catalytic mechanisms based on available crystallographic data.
• To explore the potential role of the molybdopterin ligand in enzymatic function.

Main Methods:

• Sequence alignments to identify enzyme families.
• Spectroscopic properties analysis.
• Analysis of available crystallographic structures of molybdenum-cofactor-containing enzymes.

Main Results:

• Four families of molybdenum-cofactor-containing enzymes have been identified based on sequence and spectroscopic data.
• Crystallographic structures reveal insights into active site organization and catalytic mechanisms.
• Interactions between molybdopterin and the metal center are sensitive to the metal's oxidation state.

Conclusions:

• Molybdenum-cofactor-containing enzymes utilize a conserved cofactor for redox reactions involving oxygen transfer.
• Structural data provides a framework for understanding their catalytic mechanisms.
• The molybdopterin ligand likely plays a direct role in the enzymatic mechanism due to its sensitivity to metal oxidation states.