Protein primary structure, effect activity

Besides the effect of enzyme, substrates and modulator concentrations, the catalytic potential of enzymes is affected by several environmental factors among which, pH and temperature are outstanding. These variables not only affect enzyme activity but enzyme stability as well. Enzyme stability is regarded as the capacity of the enzyme to retain its activity. Protein denaturation is an event or sequence of events leading to structural changes (not compromising its primary structure) and in most cases... 

Although all constituent amino acids of a protein may be considered important for the maintenance of an optimally folded native structure, some residues have been found to be struaurally and functionally more important than others. Residues that are directly involved in essential structure and/or function of a protein are among the most conserved, and their modifications or replacements usually result in a drastic decrease in the activity of the protein. In contrast, nonessential residues can be replaced by other amino acids and sections of polypeptides can even be removed without large negative effects on the stability of a protein. Proteins tolerate amino acid substitutions by various mechanisms (83) (a) some substitutions preserve critical interactions, (b) some interactions apparently do not make large contributions to stability, and (c) conformational adjustments occur to compensate for the changes in primary structure. 

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