= Escherichia coli fumarase C
{c}
<Escherichia coli fumarase C> is a <fumarate hydratase> of <Escherichia coli>, commonly designated FumC. It catalyzes the reversible conversion between <fumarate> plus <water> and <L-malate> in the <citric acid cycle>. The name identifies a particular enzyme, while the broader activity name can cover related catalysts.<Crystallographic studies of the catalytic and a second site in fumarase C from Escherichia coli by T. M. Weaver and others>[Abstract, stereospecific fumarate/L-malate interconversion]{ref}
The 1995 structure revealed a four-subunit assembly at $2.0\,\text{Å}$ resolution, with the <active site> formed using atoms from three chains.<The multisubunit active site of fumarase C from Escherichia coli by T. M. Weaver and others>[Abstract, tetramer and active-site placement]{ref} Further structures in 1996 used bound inhibitors and poor substrates to distinguish this catalytic A-site from a nearby B-site about $12\,\text{Å}$ away. The second site was formed by one subunit rather than three.<Crystallographic studies of the catalytic and a second site in fumarase C from Escherichia coli by T. M. Weaver and others>[Abstract, A/B-site distinction]{ref}
This gives a concrete interpretation problem for a binding experiment. Detecting a compound somewhere on the <protein> does not establish that it occupies the catalytic site. Comparing its position with substrate analogues, inhibitory behaviour and the multisubunit geometry supplies additional evidence. Similarly, a change in assembly could affect catalytic activity while retaining the same substrate-contacting <amino acid residues>. Structure and reaction-rate measurements describe complementary aspects of the working enzyme.
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