Abstract
The role of the amino acids' transamination in the tissues of fish (<i>Cyprinus carpio</i> L.) and mollusk (<i>Unio pictorum</i> L.) in homeostasis of protein metabolism under the impact of 2 and 5 maximum permissible concentrations (MPC) of Mn<sup>2+</sup>, Zn<sup>2+</sup>, Cu<sup>2+</sup> and Pb<sup>2+</sup> ions was studied. Changes in the aspartate amino-transferase (AsAT) and alanine aminotransferase (AlAT) activity under toxic impact were species-specific and depend on nature and concentration of metal in water, tissular and cellular localization of enzymes. Impact of all metals, except for Cu, caused increase of mitochondrial AsAT activity in liver and muscles of carp. Exposure to sublethal concentrations of Zn<sup>2+</sup>, Cu<sup>2+</sup>, and Pb<sup>2+</sup> ions also resulted in AsAT activation in the mitochondria of mollusk's tissues. AlAT activity in the cytoplasmic fraction of muscles and liver of both hydrobionts increased under the impact 5 MPC of all metal ions and decreased under 2 MPC. Changes of AlAT activity in mitochondria and AsAT in cytoplasm of both fish and mollusk under the impact of 2 MPC were multidirectional and determined by metal and its concentration. The transaminases' role in adaptation of the aquatic animals to the impact of heavy metal ions consists in redistribution of amino acid reserves in order to use some for ammonia detoxification (glutamate, aspartate), and others (keto acids) for energy producing to counteract the stress factor. Changes in transaminases' activity reflect the state of the organism under the impact of elevated concentrations of heavy metal ions, characterize degree of the considered hydrobionts resistance to pollution, and can also be used to predict changes in biocenoses in the contaminated areas.
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