MULTIPLE FORMS OF ENZYMES: TISSUE, ONTOGENETIC, AND SPECIES SPECIFIC PATTERNS

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Abstract
A search of the literature reveals that many different enzymes have each been resolved by physico-chemical techniques into several distinguishable molecular types. We propose to call these molecular types, isozymes. From tissue homogenates, 3 dehydrogenases (lactate, malate, and isocitrate dehydrogenase) were resolved into their component isozymes by zone electrophoresis in starch gels. The dehydrogenase isozymes were then localized on the starch by a new method that should be applicable to any electrophoretically mobile enzyme using diphosphonulcleotide or triphosphonucleotide as a cofactor. Lactate dehydrogenase obtained from the tissues of several different species were electrophoretically separated into several molecular types (isozymes) each with the same substrate specificities. The pattern of lactate dehydrogenase isozymes is species and tissue specific and changes during the embryological differentiation of the tissue. Esterase, peroxidase, and phosphatase were also resolved into separate molecular types by electrophoresis, but each of these enzymes is probably a family of enzymes the members of which have characteristic but overlapping substrate specificities. Genetic, embryological, physiological, serological considerations are presented in an effort to account for specific patterns of isozymes.