REVIEW: Structural and Functional Features of Formate Hydrogen Lyase, an Enzyme of Mixed-Acid Fermentation from Escherichia coli

K. Bagramyan and A. Trchounian^*

Department of Biophysics, Faculty of Biology, Yerevan State University, ul. Manoukiana 1, Yerevan 375049, Armenia; fax: (374-1) 55-4641; E-mail: Trchounian@ysu.am

^* To whom correspondence should be addressed.

Received January 14, 2003; Revision received February 21, 2003

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Formate hydrogen lyase from Escherichia coli is a membrane-bound complex that oxidizes formic acid to carbon dioxide and molecular hydrogen. Under anaerobic growth conditions and fermentation of sugars (glucose), it exists in two forms. One form is constituted by formate dehydrogenase H and hydrogenase 3, and the other one is the same formate dehydrogenase and hydrogenase 4; the presence of small protein subunits, carriers of electrons, is also probable. Other proteins may also be involved in formation of the enzyme complex, which requires the presence of metal (nickel-cobalt). Its formation also depends on the external pH and the presence of formate. Activity of both forms requires F₀F₁-ATPase; this explains dependence of the complex functioning on proton-motive force. It is also possible that the formate hydrogen lyase complex will exhibit its own proton-translocating function.

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KEY WORDS: formate hydrogen lyase complex, formate dehydrogenase H, hydrogenase 3, hydrogenase 4, F₀F₁-ATPase, mixed-acid fermentation, Escherichia coli

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