Proteins, changes during

Scheme 1. Proposed reaction scheme explaining how protein changes during extrusion lead to texturization of final products.

Because temperature shifts may also influence the packing quality, the temperature should not be changed during the chromatographic step and the packing of the column should be done at the operation temperature. To prevent the denaturation of sensitive proteins, the chromatography is carried out in a cold chamber (or cabinet). For this purpose the column packing has to be performed at the same ambient temperature (store the gel before use at the same temperature ). 

In addition to their protein part, most enzymes also contain a small nonprotein part called a cofactor. A cofactor can be either an inorganic ion, such as Zn2+, or a small organic molecule, called a coenzyme. A coenzyme is not a catalyst but is a reactant that undergoes chemical change during the reaction and... 

The 3 isozymes are activated by G protein-coupled receptors through two different mechanisms [2]. The first involves activated a-subunits of the Gq family of heterotrimeric G proteins (Gq, Gn, Gi4, G15/16). These subunits activate the (31, (33 and (34 PLC isozymes through direct interaction with a sequence in the C terminus. The domain on the Gqa-subunit that interacts with the (3 isozymes is located on a surface a-helix that is adjacent to the Switch III region, which undergoes a marked conformational change during activation. The second mechanism of G protein activation of PLC 3 isozymes involves (3y-subunits released from Gi/0 G proteins by their pertussis toxin-sensitive activation by certain receptors. The 3y-subunits activate the 32 and 33 PLC isozymes by interacting with a sequence between the conserved X and Y domains. 

Mailer, J. L., and Smith, D. S. (1985). Two-dimensional polyacrylamide gel analysis of changes in protein phosphorylation during maturation of Xenopus oocytes. Dev. Biol. 109 150-156. 

Sidney Altman discovered this property of RNA in the course of studies on precursor transfer RNA. It was realized that the catalytic properties of RNA are not exactly the same as those of protein enzymes, since the ribozyme is itself active and thus undergoes change during the catalytic reaction. This does not correspond to the generally accepted definition of an enzyme. Later studies, however, showed that some ribozymes are capable of acting catalytically at other RNA molecules. The ribozymes remain completely unchanged in this process, and thus fulfil the definition of a real enzyme. 

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