Biosynthesis of Tetrapyrroles

Abstract

In 1978 Gunsalus and Wolfe isolated from methanogenic bacteria – anaerobic archaebacteria - a yellow low-molecular weight substance which they named factor 430 because of its absorption maximum at 430 nm. Ellefson, Whitman and Wolfe discovered that F430 is the prosthetic group of methyl coenzyme M reductase, the enzyme that catalyzes the final step in methane formation. F430 thus has coenzyme function. Until now coenzyme F430 has been found only in methanogenic bacteria, in which it is always present. The primary structure of methyl coenzyme M reductase, which contains three different subunits, has been determined via analysis of the encoding genes. With knowledge of the structure of coenzyme F430 and of the amino acid sequence of the protein subunits the groundwork has been laid for further structural analysis of methyl coenzyme M reductase. Insight into the three-dimensional structure of the enzyme is a prerequisite for a detailed understanding of the role of the novel tetrapyrrole in the catalysis of methane formation.