Hydrogenases and H(+)-reduction in primary energy conservation

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Hydrogenases are metalloenzymes crucial for hydrogen metabolism.
• They are classified into [NiFe], [FeFe], and Hmd hydrogenases based on active site composition and phylogenetic distinctiveness.
• These enzymes contain iron-sulfur clusters, except for the Hmd class found in methanogenic archaea.

Purpose of the Study:

• To review the classification of hydrogenases based on phylogenetic analysis.
• To correlate hydrogenase function with different phylogenetic groupings.
• To discuss the potential role of [FeFe]hydrogenases in eukaryotic cell origins and their relationship with respiratory complex I.

Main Methods:

• Phylogenetic analysis of hydrogenase protein sequences.
• Functional characterization of different hydrogenase classes and subgroups.
• Comparative structural and functional analysis with respiratory electron transport chain components.

Main Results:

• [NiFe]hydrogenases are subdivided into four functional subgroups involved in H(2) uptake, sensing, bidirectional catalysis, or energy conversion.
• [FeFe]hydrogenases form a homogeneous group primarily involved in H(2) evolution.
• Structural and functional similarities exist between hydrogenase subunits and complex I of the respiratory chain.

Conclusions:

• Phylogenetic classification provides a framework for understanding hydrogenase diversity and function.
• The study highlights the evolutionary significance of hydrogenases, particularly [FeFe]hydrogenases, in early cellular life.
• Understanding these relationships offers insights into bioenergetics and the evolution of complex cellular machinery.