Final answer:
Isozymes are differentially expressed enzymes that carry out the same reaction within a species, while interspecific enzyme homologs are similar enzymes found in different species. They differ in molecular weight, charge, isoelectric pH, substrate specificity, and kinetic properties like Km and Vmax.
Step-by-step explanation:
Isozymes and interspecific enzyme homologs differ in several properties including molecular weight, charge, isoelectric pH, substrate specificity, and tertiary structures. Isozymes are enzymes that catalyze the same chemical reactions but are coded by different genes and are often found in different tissues within the same species. A classic example is lactate dehydrogenase (LDH), which has five isoenzyme forms, each made up of different combinations of 'H chain' and 'M chain' polypeptides. Interspecific enzyme homologs, on the other hand, refer to similar enzymes found in different species that may have diverged in their properties due to evolutionary changes.
One crucial aspect of isozymes is that they can serve as a medical diagnostic tool by indicating tissue or organ-specific damage, as each type of LDH isozyme is prominent in different parts of the body. Importantly, enzyme specificity is a significant differentiator, which is further classified into various types: absolute specificity, where an enzyme acts on one particular substrate; relative specificity, where an enzyme acts on one particular bond; group specificity, where an enzyme acts on a specific functional group, irrespective of the structure of the rest of the molecule; and reaction specificity, where enzymes are specific for the type of reaction they catalyze, regardless of the substrate.
Moreover, kinetic properties such as Km (substrate affinity) and Vmax (maximum reaction rate) often differ between isozymes as well as among interspecific homologs, which can affect their behavior under cellular conditions and their response to allosteric regulation and inhibitors. These differences are essential for understanding how these enzymes function in different environments and under different physiological conditions.