Aminotransferases definition

Are these so-called organelle-specific isoenzymes really isoenzymes in the true sense Comparative arguments based on the existence of true organelle-specific isoenzymes in animals seem persuasive. However, it must be emphasized again that here, as in so many other aspects of the biochemistry of plant aminotransferases, definite conclusions must wait until more homogeneous enzyme preparations are available for study. 

The serum enzymes ALT, AST, and alkaline phosphatase are also important indicators of chemically induced heptotoxicity in experimental animal studies. An additional heptocyte enzyme, sorbitol dehydrogenase (SDH), is also used frequently as a more sensitive complement to the aminotransferases. In experimental studies, histopathology is the most definitive indicator of injury and is highly informative about mechanistic events. 

Because few plant enzymes have been purified to a homogeneous state, final and definitive conclusions cannot yet be drawn concerning their substrate specificities. Many aminotransferase preparations hitherto studied have not shown absolute specificity for a single amino donor compound or amino acceptor compound. Where an incompletely purified enzyme catalyzes a multiplicity of reactions, it is obviously difficult to be certain whether the reactions are all being catalyzed by the same enzyme or by different enzymes present in the preparation. With this reservation, it is nevertheless possible to draw a number of conclusions from currently available data. The outer limits of specificity can fi-equently be ascertained, even though it may sometimes be found subsequently that purer preparations will exhibit more restricted substrate specificities. 

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