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Thermoalkalophilic lipases are the dimeric enzyme. At the dimer interface of the thermoalkalophilic lipase, a structural zinc site is located containing zinc ion. That means it is a zinc-containing metalloenzyme. This enzyme is prone to aggregation and the structural zinc site is the one that has been shown to induce the aggregation.
A team of researchers from the faculty of Natural Science and Engineering, Molecular Biology, Genetics and Biochemistry, Sabanci University, Turkey has explained the interplay between zinc and aggregation of the thermoalkalophilic lipase isolated from Bacillus thermocatenulatus. They took Bacillus thermocatenulatus as a model organism for this enzyme.
They found out that zinc removal from the dimer interface structural zinc site caused thermoalkalophilic lipase dime to form monomer and reduced the thermostability. This result clearly reveals that there is a link between zinc and the dimerization of the enzyme subunits to achieve thermostability. However, when researchers added zinc to the enzyme externally, they found enzyme aggregated into a cluster-like structure.
Using biochemical and kinetic characterizations of the enzyme aggregates induced by zinc, researchers found that aggregates from late and early stages of aggregation have different characteristics. That means, in the early aggregation stage, aggregates were soluble with native-like structure while at the late aggregation stage aggregates became insoluble with Fibrillar characteristics showing the binding affinity towards Thioflavin T (ThT) and Congo Red.
The Researchers also performed the impact of temperature on the enzyme aggregation induced by zinc and found that the native-like early aggregates are reversible. That means the native-like early aggregates can dissociate into functional enzyme at a higher temperature while dissociation of the aggregates of the late aggregation stage was limited.
In conclusion, zinc-induced aggregation of the thermoalkalophilic lipase is reversible by temperature switches which can cause aggregates at the early aggregation stage to gain a functional form of the enzyme.
Reference: American Chemical Society
Article DOI: 10.1021/acs.biochem.5b00200