mutation in Mucanote lactonizing enzyme can be caused due to the deletion in catB structural gene and loss of pleiotropic activities of both the catB and catC gene. A microorganism named Pseudomona putida loses its ability to grow due to the deletion in catB gene for muconate lactonizing enzyme. Pseudomona putida (a cold sensitive mutant) normally grows at 30 degree C, but due to the result in the mutation of cis, cis-muconate lactonizing enzyme, it loses its ability to also grow at 15 degree C. At the low temperature, the mutant enzyme does not lose its function, rather the structural gene that codes for that particular enzyme loses its capability of expressing its gene at that temperature. Additionally, mutation can also lead to the change in the structure and function of the enzyme. The different structure that is resulted by the mutation in the muconate lactonizing enzyme is Cl-muconate lactonizing enzyme. Cl-muconate lactonizing enzyme has two types of conformations :- open and closed. The mutation results in the switch of an amino acid to Ser99 and it hydrogen bonds to Gly48. The structure that results due this has a closed active site. Therefore, this change from muconate lactonizing enzyme to Cl-muconate lactonizing enzyme results in dynamic differences in the binding capability of the active site. Finally, a change in the binding capability will not let the reaction of dehalogenation to proceed any further. One important aspect to notice is that there cannot be a conformational change in Gly48 to Thr52. This is because the polypeptide will not be able to twist if Gly48 was replaced. Also, Thr52 and Glu50 are hydrogen bonded together. Additional change in the conformation due to the mutation of the muconate lactonizing enzyme can result in a 21-30 loop. This can lead to a major difference in the active sites because it shows the difference in the polarity of an amino acid. In Cl-muconate lactonizing enzyme, Ile19 and Met21 are less polar compared to His22 (same position as Ile19) for muconate lactonizing enzyme. Hence, this results into the difference in the hydrophobic core structure at the active site. Enzymes are very specific to their substrates and the formation of the product is dependent on the enzyme-substrate activity. The point mutation that resulted into the variants, Ser271Ala and Ile54Val, for Cl-muconating enzyme showed a significant decrease in the dehalogenation activity. One advantage of the mutation in muconate