Final answer:
LDH is an enzyme with five isoenzyme forms, functioning differently in various tissues. Each form is composed of four polypeptide chains, which are combinations of 'H' and 'M' types, controlled by genes on chromosomes 11 and 12. The study of these enzymes is important in clinical diagnostics and understanding enzyme structure and function.
Step-by-step explanation:
LDH is an enzyme that catalyzes the conversion of lactate to pyruvate, and exists in multiple isoenzyme forms. These isoenzymes are tetramers, being made up of four polypeptide chains consisting of two different types: 'H chain' (H-form), and 'M chain' (M-form). These subunits are encoded on chromosomes 11 and 12 respectively. The combination of these chains results in the five isoenzyme forms of LDH, each with variations in physical characteristics such as molecular weight, electrophoretic mobility, and Km (Michaelis constant).
As explained in medical and biological literature, the presence of different isoenzyme forms allows LDH to function effectively in a variety of tissue types. For example, muscle tissues predominantly contain M-type chains, while heart tissues have a higher concentration of H-type chains. Understanding the structure and function of these enzymes plays a role in clinical diagnostics, where distinct patterns in LDH isoenzymes can indicate specific tissue damage.
In the context of immunoglobulins, light chains and heavy chains have similar structural components like variable (V) and constant (C) regions as well as domains that contribute to the functionality of the antibodies. The difference in the sequence and number of amino acids contributes to the specificity and various classes of immunoglobulins, notably the four subclasses of IgG.