Stabilization of industrial enzymes became an important research topic due to the inactivation problem during all the stages of enzyme production, purification, storage and applications.

One of the methods used to increase stability of protein molecules is crosslinking, a chemical modification technique, in which two chemical groups of protein molecules are covalently bonded by using a crosslinker. Dimethyl suberimidate (DMS) is a homobifunctional bisimidoester having an 11 Å crosslinking distance which selectively crosslinks amino groups to each other.

Citrate synthase (EC 4.1.3.7) catalyzes the reversible condensation of acetyl-CoA to form citryl-CoA, which is subsequently hydrolyzed to yield citrate and coenzyme A. Pig citrate synthase is a dimer of two identical subunits and has a molecular weight of about about 100,000 Da.

Pig citrate synthase was used as a model enzyme, crosslinked with DMS and the effects of DMS-croslinking on its activity and thermal stability were investigated. First of all, DMS-crosslinking did not alter the enzyme activity. First order inactivation was observed for both the native and DMS-crosslinked enzymes in the range of 30 - 40°C. Crosslinking decreased the inactivation constants of the enzyme under all the conditions used and half-life values of the enzyme increased approximately 1.5 times at different temperatures.