Structure and Function of Aspartate Aminotransferase

Department of Medical Chemistry, Osaka Medical College Takatsuki, Osaka 569, Japan 

AspAT is a PLP-dependent enzyme. This dimeric enzyme contains one PLP per subunit whose molecular weight is about 50,000. 

KFKRDNQLEYKP----NEIIVGVGAKHVLYTLFQVILNEG--D-EVII PI PYWVSYPEQVKLAGG—VPVYIEATS — EQNYK 

PcAsp LEALKT PGTWNHITDQIGM FS FTGLN PKQVE—YLINEKHIYLLPSG---RINMCGLTTKNLDYVATSIH EAVTKIQ 

HcAsp LEALKTPGTWNHITEQIGMFS FTGLN PKQVE—YLVNQKHIYLLPSG-----RINMCGLTTKNLDYVATSIHEAVTKFQ 

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Fasella P and Turano C (1970) Structure and catalytic role of the functional groups of aspartate aminotransferase. Vitamins and Hormones 157-94. 

Liver. In humans, chronic Cd exposure does not typically result in hepatotoxicity. In laboratory animals, the liver accumulates the largest concentrations of Cd after acute or chronic exposures. In chronically exposed rats, liver injury occurs prior to renal dysfunction. Chronic Cd effects in the liver include increased plasma activities of alanine and aspartate aminotransferases, structural irregularities in hepatocytes, and decreased microsomal mixed function oxidase and CYP450 activities. Acute exposures in rats result in hepatic necrosis, particularly in parenchymal cells. Additionally, rough endoplasmic reticulum deteriorates, while smooth endoplasmic reticulum proliferates. Mitochondria are also degraded. As is the case with chronic exposure, microsomal mixed function oxidases and CYP450s are inhibited. 

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