LIS - Legume Information System
Information about legume traits for crop improvement
GlycineMine
v5.1.0.3
Glycine data from LIS
v5.1.0.3
Glycine data from LIS
| Type | Active_site |
| Description | Citrate synthase is a member of a small family of enzymes that can directly form a carbon-carbon bond without the presence of metal ion cofactors. It catalyses the first reaction in the Krebs' cycle, namely the conversion of oxaloacetate and acetyl-coenzyme A into citrate and coenzyme A. This reaction is important for energy generation and for carbon assimilation. The reaction proceeds via a non-covalently bound citryl-coenzyme A intermediate in a 2-step process (aldol-Claisen condensation followed by the hydrolysis of citryl-CoA). Citrate synthase enzymes are found in two distinct structural types: type I enzymes (found in eukaryotes, Gram-positive bacteria and archaea) form homodimers and have shorter sequences than type II enzymes, which are found in Gram-negative bacteria and are hexameric in structure. In both types, the monomer is composed of two domains: a large α-helical domain consisting of two structural repeats, where the second repeat is interrupted by a small α-helical domain. The cleft between these domains forms the active site, where both citrate and acetyl-coenzyme A bind. The enzyme undergoes a conformational change upon binding of the oxaloacetate ligand, whereby the active site cleft closes over in order to form the acetyl-CoA binding site [ ]. The energy required for domain closure comes from the interaction of the enzyme with the substrate. Type II enzymes possess an extra N-terminal β-sheet domain, and some type II enzymes are allosterically inhibited by NADH [].This entry represents types I and II citrate synthase enzymes, as well as the related enzymes 2-methylcitrate synthase and ATP citrate synthase. 2-methylcitrate ( ) synthase catalyses the conversion of oxaloacetate and propanoyl-CoA into (2R,3S)-2-hydroxybutane-1,2,3-tricarboxylate and coenzyme A. This enzyme is induced during bacterial and fungal growth on propionate [ , ], while type II hexameric citrate synthase is constitutive []. ATP citrate synthase () (also known as ATP citrate lyase) catalyses the MgATP-dependent, CoA-dependent cleavage of citrate into oxaloacetate and acetyl-CoA, a key step in the reductive tricarboxylic acid pathway of CO2 assimilation used by a variety of autotrophic bacteria and archaea to fix carbon dioxide [ ]. ATP citrate synthase is composed of two distinct subunits. In eukaryotes, ATP citrate synthase is a homotetramer of a single large polypeptide, and is used to produce cytosolic acetyl-CoA from mitochondrial produced citrate []. This entry includes citrate synthase from Thermosulfidibacter takaii, which catalyses both citrate generation and citrate cleavage as it is part of a reversible tricarboxylic acid (TCA) cycle that can fix carbon dioxide autotrophically and may represent an ancestral mode of the conventional reductive TCA (rTCA) cycle [].There are a number of regions of sequence similarity between prokaryotic and eukaryotic citrate synthases. One of the best conserved contains a histidine which is one of three residues shown to be involved in the catalytic mechanism of the vertebrate mitochondrial enzyme [ ]. This entry represents this region. |
| Short Name | Citrate_synthase_AS |
