Isoenzymes and Ontogeny

Abstract

Summary 1. In this review, representative data on the nature of enzyme multiplicity and the developmental progressions of multiple enzyme forms have been collected, and the significance of this material has been discussed in relation to gene involvement during tissue differentiation. 2. In addition, emphasis has been directed towards the relevance of this onto‐genetic information to a wide variety of biological phenomena, such as the possibilities of metabolic advantage conferred by the distinctive properties and physiological locations of these multiple enzyme forms, the insight into the subunit structure and compositional interrelationships of proteins, the aetiology of disease states, the relationship to hormone action, the extra nuclear specification of enzymes, and the transformations between particulate and soluble enzymes. 3. Three isoenzyme systems in particular have been chosen for the special development of these themes and treated in some detail; lactate dehydrogenase (LDH), aldolase and the esterases. Briefer accounts of the ontogeny of other less‐studied series of multiple enzyme forms have also been included. 4. In relation to LDH, the major findings and conclusions of the pioneering investigators have been outlined, together with the reassessments which have been necessitated by recent studies of LDH ontogeny. It is evident, for example, that the early embryonic form of this enzyme is not necessarily parental as previously thought, and the realization appears to possess wide‐ranging implications in regard to the control of synthesis of the enzymes. An indirect role of oxygen in LDH biosynthesis is indicated together with the independent regulation of the separate genes. 5. Recent developments in the enzymology of preimplantation ova have been discussed. It is noteworthy that the extraordinary levels of LDH activity which have been reported to be associated with these early developmental stages, may arise by extracellular adsorption rather than by an intrinsic synthesis of enzyme. Hence contemporary interest in this area has shifted towards a comprehension of the biochemical significance of the extremely unusual, selective concentrations of extracellular lactate dehydrogenase in the oviduct, the relation of this enzyme to the specialized growth requirements of the ova, and the influences of reproductive hormones on these oviducal isoenzymes. 6. The role of aldolase ontogeny as well as the composition, gene control, and native state of these lysases is also reviewed. This enzyme provides a particular example of the manner in which tissue modification of the catalytic and structural properties of enzymes may influence interpretations of the native state of purified proteins, and in this case, also, the observable microheterogeneity satisfies previous disquietude in regard to the existence of different subunits in the muscle enzyme. 7. The basic developmental importance of aldolase‐C is stressed by the occurrence of this form of the enzyme in the early embryos of many different species. Furthermore, a ...

Isoenzyme-specific thermostability of human cytosolic creatine kinase

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Isoenzymic Analysis of Fifteen Non-Lysosomal Enzymes in Human Chorionic Villi

“…The importance of isoenzymic studies during development was soon appreciated [2][3][4][5][6]. However, most available data are de rived from studies of fetuses over 3 months of age or from placenta at full term.…”

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