Enzymes conformational characteristics

Theoretically, all of the proteinaceous inhibitors act by presenting a loop portion of their chains as an idealized, that is, pre-organized for optimal interactions, substrate for elastase. Conformational analysis of the inhibitor residues P P3 and P1-P3 for a series of proteinaceous, serine protease inhibitors showed that there is little difference between their free and/or complexed states [63]. In aj-PI, the loop contains as its elastase reactive center (see Table 2.2) a Met-Ser linkage. The importance of the P,-substituent in a PI for its enzyme specificity characteristics is exempli-... 

Synthetic poly(amino acids) possess advant s as well as disadvantages as enzyme models, when compared widi vinyl polymers. The greatest advantage is probably the structural similarity of the polymer backbone (polypeptide linkage), and conformational characteristics derived therefrom. On the odier hand, die syndietic problems are much greater than those of vinyl polymers. A review artide was recently published on tfiis subject (726). 

Very valuable information on the energy and conformation characteristics of ccDNA has arisen from experiments in which the value of Lk could vary, and the equilibrium distribution of the cc molecules over the Lk value was studied. The most convenient way to vary Lk is to employ special enzymes we have already mentioned above, the topoisomerases. The studies under discussion employed type I topoisomerases, which alter the topological state of ccDNA by breaking and rejoining only one of the strands of the double helix. The mechanism of action of these enzymes has been elaborated in great details (Wang, 1996 [86]). These enzymes relax the distribution of the molecules over the Lk value to its equilibrium state. The very sensitive gel- electrophoresis method was used to analyze the distribution of the ccDNA molecules over the Lk value. This method can easily separate two molecules of ccDNA that differ in Lk just by one. 

The anomalous activity characteristics have been attributed to conformational changes of the solubilized enzyme [49], but more recent spectroscopic studies seem to indicate that this is not the main cause. Solubilization of an enzyme into microemulsion droplets does not normally lead to major conformational alterations, as indicated, e.g., by fluorescence and phosphorescence spectral investigations [28,50]. The situation is complex, however, and it has been shown by circular dichroism (CD) measurements that the influence of the oil/water interface on enzyme conformation may vary even between enzymes belonging to the same class [51]. In the case of human pancreatic lipase, the conformation of the polypeptide chain is hardly altered after the enzyme is transferred from a bulk aqueous solution to the microenvironment of reverse micelles. Conversely, the CD spectra of the lipases from... 

Enzymes are proteins, i.e. sequences of amino acids linked by peptide bonds. The sequence of amino acids within the polypeptide chain is characteristic of each enzyme. This leads to a specific three-dimensional conformation for each enzyme in which the molecular chains are folded in such a way that certain key amino acids are situated in specific strategic locations. This folded arrangement, together with the positioning of key amino acids, gives rise to the remarkable catalytic activity associated with enzymes. 

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