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From biodiversity to biotechnological aspect, scientific investigation related to enzyme produced by microorganism has increasingly attention. Enzymes from different place; temperature dependent, will have different behavior and properties. For instant, when enzymes from mesophilic or thermophilic organisms are submitted to cold temperature, rigidification of their structure may cause a loss their activity. However, the cold-adapted enzymes from psychrophilic microorganisms living at temperature close to the freezing point of water encountered in, and generally exhibit a higher activity at low temperatures and a lower thermal stability than their mesophilic counterparts. The properties of cold-adapted enzymes make them potentially valuable alternatives to their mesophilic counterparts. To answer the question how the structural motions of enzymes contribute to their catalytic activities, the investigation of enzyme behaviour or ability to undergo efficient catalysis at low temperature is a crucial step achieved by the determination of kinetic and thermodynamic parameters of the catalytic reaction in a wide range of temperatures, and by the comparison of these parameters with those from a related mesophilic enzyme investigated in the same conditions. Enhancement of the catalytic activity of the catalytic activity of psychrophilic enzymes is generally attributed to an increased flexibility of some of their structural components, leading to, generally, a reduction of their thermostability. In case for the glucokinase enzyme from psycophropilic bacteria have higher activity and higher thermostability. However, generally, the low stability of cold-adapted enzyme should be the consequence of structural changes raised from the strong selection pressure allowing a viable physiological activity at low temperature. Flexibility of cold-adapted enzymes remains the main adaptive character of psychrophilic enzymes, responsible for the decrease of activation enthalpy (∆H*) that efficiently increases kcat at low temperatures. For examples, data noticed that the β8-9 turn regions of psychrophilic subtilisins are more flexible than those mesophilic counterpart, however affected to the thermostability. We summarized that, the increasing of engineered flexibiliy of psychrophilic enzyme contribute to the decreased thermal stability and further increased the catalytic reaction of enzyme. How the decreasing of activation enthalpy can increase the kcat. This equation explained the answer.
k = ƙkB T/h exp (-∆G*/RT),
in which k is the catalytic constant, kB is the Boltzmann constant, T is the temperature in Kelvin, ∆G* is the activation energy, R is the gas constant, and ƙ is the transmission coefficient which is in general misleadingly considered to be equal to 1. From this equation, ne can readily appreciate the importance of the value of the activation energy on the reaction rate. Indeed, if one assumes a value of ∆G*= 40 kJ/mol, a decrease of only 10% of this value will increase the reaction rate by a factor of nearly 2. This underlines the importance of catalysts such as enzymes, the basic action of which is to decrease the activation energy of a chemical reaction. A very efficient enzyme will bring the activation energy close to zero, in which case the exponential term will tend to 1 and the reaction will become nearly independent of temperature. An important consequence is that the lower the activation energy, the lower the thermodependence of the reaction rate. This has to be considered as of prime importance in the context of cold adapted enzyme that by increasing of engineered flexibility of enzyme at low temperature, is to develop an enzyme that either decreases the activation enthalpy of the reaction or increase the activation entropy, because:
∆G*= ∆H*-T∆S*
Protein science or its research techniques closely related and contributed to my research. My research title is related to bioremediation and biodegradation of crude oil by fungi screened from nature. We screened and isolated the fungi from oil contaminated site and applied these fungi to oil contaminated site. In addition, enzyme activities such as, cathecol 1,2-dioxyganes (C12O), cathecol 2,3-dioxygenase (C23O), laccase, manganese peroxidase, and lignin peroxidase, that responsible in biodegradation were measured and we analyzed the close relationship between this enzyme and biodegradation yield. However, recently, the oil contamination in Artarctic and other place that the temperatures close to or below 0oC has been reported. By the screening method, we can isolate oil degrading microorganism from these kind of place. By the protein science and its research techniques, we can analyzed the differences and the relationship of enzyme activities especially, C12O, C23O, laccase, manganese peroxidase and lignin peroxidase activities to their mesophilic enzymes. However, high activities of these enzymes at low temperature are highly expected by the researcher concerned in bioremediation and biodegradation of crude oil in low temperature area.