Cold-active citrate synthase (CS) from an Antarctic bacterial strain DS2-3R (Ds)-like. CS catalyzes the condensation of acetyl coenzyme A (AcCoA) and oxalacetate (OAA) to form citrate and coenzyme A (CoA), the first step in the citric acid cycle (TCA or Krebs cycle). 2-methylcitrate synthase (2MCS) catalyzes the condensation of propionyl-coenzyme A (PrCoA) and OAA to form 2-methylcitrate and coenzyme A (CoA) during propionate metabolism. The overall CS reaction is thought to proceed through three partial reactions: a) the carbanion or equivalent is generated from AcCoA by base abstraction of a proton, b) the nucleophilic attack of this carbanion on OAA to generate citryl-CoA, and c) the hydrolysis of citryl-CoA to produce citrate and CoA. DsCS, compared with CS from the hyperthermophile Pyrococcus furiosus (not included in this group), has an increase in the size of surface loops, a higher proline content in the loop regions, a more accessible active site, and a higher number of intramolecular ion pairs. This group contains proteins which functions exclusively as either a CS or a 2MCS, as well as those with relaxed specificity which have dual functions as both a CS and a 2MCS. For example, included in this group are Corynebacterium glutamicum (Cg) PrpC1 and -2, which are only synthesized during growth on propionate-containing medium, can use PrCoA, AcCoA and butyryl-CoA as substrates, and have comparable catalytic activity with AcCoA as the major CgCS (GltA, not included in this group).