Isoenzymes, also termed isozymes, constitute multiple molecular forms of an enzyme that occur naturally within a single species and catalyze the same chemical reaction while differing in their primary protein structure ^[1]. The structural multiplicity originates from genetically determined variation, including the expression of distinct gene loci, allelic variants, or heteropolymeric assemblies of non-covalently associated polypeptide chains ^[1]. These genetically encoded differences in primary structure give rise to modifications in higher-order structure, which in turn produce distinguishable kinetic parameters, substrate affinities, regulatory responses, and subcellular distributions among the forms ^[2][3]. Operationally, isoenzymes are enzyme proteins that share the same catalytic activity but are separable by suitable physical methods such as electrophoresis, a criterion that permits their experimental resolution and characterization. Within the structural and functional framework of enzymology, the concept designates a defined class of naturally occurring enzyme variants whose multiplicity is rooted in genetic control of protein structure, and whose individual forms exhibit characteristic structural and functional profiles that are subject to direct experimental measurement ^[1]. The term encompasses forms arising from independent genetic loci, allelic variation, and hybrid assembly of distinct subunit types, thereby providing a structural basis for the differential functional roles observed among multiple enzyme forms ^[1][2].