Aspartate aminotransferase isozymes

E., 1978 Studies on the selective permeation of radioactivelly labelled aspartate aminotransferase isozymes into mitochondria in vitro, Eur.J.Biochem.,... 

Two compounds other than the natural substrate SAM, l-VG and S -methyl-L-methionine (SMM), have been described so far as both substrates and inhibitors of ACS isozymes. l-VG was isolated 30 years ago from the fungus Rhodophyllus nidorosus It was shown to be a mechanism-based inhibitor of aspartate aminotransferase and kynurenine aminotransferase. First of all, l-VG is an alternative substrate of ACS in addition to being an inhibitor as described in the previous section. ... 

N3. Nisselbaum, J. S., Effect of phosphate and other anions on measurement of the activities of the isozymes of rat liver aspartate aminotransferase. Anal. Biochem. 23, 173-181 (1968). ... 

Although CK and LD isozymes and myoglobin are sensitive biomarkers of skeletal muscle injury, they are also found in cardiac muscle and thus are not tissue specific. Cardiotoxicity must be excluded in order to use them effectively as biomarkers. Injured muscle releases other enzymes in significant amounts, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and aldolase however, these also lack tissue specificity. 

Biosynthesis metabolism Asp is formed from oxaloacetic acid by aspartate aminotransferase (EC 2.6.1.1) and serves as starting material in the biosyntheses of threonine, methionine, and lysine. The first step is catalysed by aspartate kinase (EC 2.7.24) which only occurs in plants and microorganisms. This enzyme exists as 3 isozymes in Escherichia coli and exhibits a typical example of feedback regulation. Asp plays a central role in the biosyntheses of pyrimidines and purines. In the urea cycle Asp condenses with " citrulline to aigininosuccinate, a stimulating neuro-transmitter. ... 

Aspartate transaminase (AST) (also known as glutamic oxaloacetic transaminase, or GOT), the most active of the aminotransferases, is found in most cells. Because AST isozymes occur in both mitochondria and the cytoplasm and the reaction that it catalyzes is reversible, this enzymatic activity significantly influences the flow of carbon and nitrogen within the cell. For example, excess glutamate is converted via AST to aspartate. Aspartate is then used as a source of both nitrogen (for... 

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