Final answer:
Multiple forms of an enzyme catalyze the same reaction but differ in physical properties and tissue distribution. Enzymes are specific to substrates based on the lock-and-key or induced fit models and can be regulated allosterically for precise metabolic control.
Step-by-step explanation:
Multiple molecular forms of an enzyme are similar in that they catalyze the same chemical reaction but differ in their physical properties such as molecular weight, charge, electrophoretic mobility, Km (Michaelis constant), and isoelectric pH. For example, lactate dehydrogenase (LDH) exists in five isoenzyme forms, which are combinations of two types of polypeptides, the 'H chain' and 'M chain,' making up a tetramer structure. Each LDH isoenzyme has a specific combination of these chains, leading to their distinct properties and allowing differential expression in tissues based on metabolic needs.
Regarding enzyme functionality, each enzyme molecule has an active site which is specific to its substrate, following the lock-and-key model, suggesting a perfect fit between the enzyme and its substrate. Alternatively, the induced fit model allows for slight conformational changes in the enzyme to accommodate the substrate, enabling some enzymes to act on a variety of structurally related substrates.
Enzymes are intrinsically flexible molecules that can undergo allosteric regulation, where binding of molecules at sites distinct from the active site can lead to conformational changes that affect the enzyme's activity. This regulation, combined with the specificity and induced fit of enzymes, results in highly controlled and efficient biochemical pathways within the cell.