title: Enzyme polymorphism and function during embryonic development.
abstract: Alterations in multiple molecular forms of enzymes have been described during normal embryogenesis. Changes in electrophoretic patterns, which differ from the normal isozyme ontogeny, occur in embryos and their yolk-sacs during incipient maldevelopment secondary to teratogen exposure. One such isozyme change, in response to a teratogenic regimen using 9-methyl pteroylglutamic acid (PGA), is persistence of lactate dehydrogenase-5 (LDH-5) beyond its time of normal involution in the rat yolk-sac. Since LDH-5 is an allosteric regulatory enzyme which favors anaerobic metabolism, the cellular respiration of 9-methyl PGA-treated embryos was investigated and found to be depressed. However, no changes were found in the oxidative metabolism of visceral yolk-sacs from similarly treated pregnancies. A possible explanation for the unchanged oxygen consumption is the observed simultaneous quantitative alterations in other LDH-yolk-sac isozymes following 9-methyl PGA treatment. Other potential causes include known changes in isozymes other than LDH, limitation of enzyme function by its substrate or co-factor or the presence of a functionally inert LDH-5 isozyme. Changes in LDH and other isozyme patterns and their associated metabolic alterations may eventually prove useful in predicting chemical teratogenicity.
mesh_terms: D000818:Animals; D004622:Embryo, Mammalian; D004798:Enzymes / Q000502:physiology*; D005260:Female; D005492:Folic Acid / Q000009:adverse effects / Q000032:analysis; D007527:Isoenzymes; D007770:L-Lactate Dehydrogenase / Q000009:adverse effects; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D014817:Vitelline Membrane / Q000166:cytology / Q000187:drug effects
chemical_list: D004798:Enzymes; D007527:Isoenzymes; D005492:Folic Acid; D007770:L-Lactate Dehydrogenase