Enzyme-specific Conservation Patterns

The next paragraphs try to interpret frequently occurring classes of conservation patterns , meaning the set of totally invariant or at least highly conserved positions in a family alignment. 1Tie conservation patterns of enzyme families are different from those of non-catalytic proteins and can be used for enzyme identification and classification. 

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From what was said in the previous paragraphs, it appears that the specific conservation pattern of a protein family can be used to predict whether the proteins are enzymes, bind metal ions, or rather have a structural or regulatory role. If the proteins are known to be enzymes, the conservation pattern can be used to predict which residues are part of the active site, and possibly also which catalytic mechanism is being used. For example, it would be straightforward to submit a family of structurally uncharacterized proteases to that type of analysis in order to find out whether they are serine proteases, aspartate proteases, metalloproteases, or if they belong to a different class. Moreover, it is possible to compare the family s conservation pattern with those of other, better characterized enzyme families this approach will be discussed in more detail in Sect. 5.6. 

Each monomer contains one pyridoxal phosphate and a highly conserved primary structure in the vicinity of the cofactor binding site. The enzymes follow the same catalytic mechanism, a rapid equilibrium random Bi Bi mechanism. However, unlike animal phosphorylases, the microbial and plant enzymes are not subjected to covalent or allosteric control. Within the group of higher plant phosphorylases two types of enzyme have been distinguished which differ in monomer size, peptide pattern, glucan specificity, and intracellular location (1-3). Based on immunochemical studies on leaf tissues (4-5), one enzyme form has been localized in the cytosol whereas the other one resides in the chloroplast. Thus, the two plant phosphorylase types represent non-interconvertible proteins which presumably have entirely different metabolic functions. 

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