Heart aspartate transaminase

Q4 Cardiac enzymes are released into the blood following heart muscle damage during a heart attack. Creatine kinase, particularly its MB isoenzyme, is one of the most specific of these enzymes, which reaches a peak 24 hours after infarction. It rises and then falls within the first 72 hours of the heart attack. Aspartate transaminase is also released, but levels of this enzyme can be raised in several other conditions, so it is less specific than creatine kinase MB. Troponin T is also specific for myocardial damage and is raised for approximately two weeks following infarction. Finding a high concentration of these enzymes in a patient s blood therefore supports the evidence obtained from the ECG and confirms that the patient has suffered a myocardial infarction. 

Heart attack or liver disease (cirrhosis, hepatitis) Lactate dehydrogenase (LDH) Aspartate transaminase (AST)... 

Transaminases participate in metabolism of most of the amino acids, over 60 different enzymes have been identified.142163 Best studied are the aspartate aminotransferases, a pair of cytosolic and mitochondrial isoenzymes which can be isolated readily from animal hearts. Their presence in heart muscle and brain in high concentration is thought to be a result of their functioning in the malate-aspartate shuttle... 

Transaminases Alanine aminotransferase (ALT) Aspartate aminotransferase (AST) Liver, heart, skeletal muscle 0 0 lU/L 0 0 lU/L Raised levels indicate hepatocyte damage/necrosis ALT is more liver specific but has a longer half-life, so less sensitive May be normal in compensated liver cirrhosis... 

Myocardial infarction occurs when the blood supply to the heart muscle is blocked for an extended time. If this lack of blood supply, called ischemia, is prolonged, the myocardium suffers irreversible cell damage and muscle death, or infarction. When this happens, the concentration of cardiac enzymes in the blood rises dramatically as the dead cells release their contents into the bloodstream. Although many enzymes are liberated, three are of prime importance. These three enzymes, creatine phosphokinase (CPK), lactate dehydrogenase (LDH), and aspartate aminotransferase/serum glutamate-oxaloacetate transaminase (AST/SGOT), show a characteristic sequential rise in blood serum level following myocardial infarction and then return to normal. This enzyme profile, shown in the ac-... 

Commercial preparations of pig heart glutamate-oxaloacetate transaminase have been screened for their ability to transaminate various a-keto acids with l-[ N]glutamate (32). In addition to l-[ N]aspartate, enzyme preparations were able to catalyze the formation of labeled tyrosine, phenylalanine, leucine, and dihydroxyphenylalanine, as demonstrated by HPLC (17). However, these amino acids have not yet been obtained in radiopure form by this method. The -keto acid analogs of valine and tryptophan were not transaminated by the enzyme preparations. Glutamate-oxaloacetate transaminases obtained from several commercial sources have varying abilities to transaminate the -keto acid... 

Perfused heart incorporates at high level into C-2, C-3, and C-4 of glutamate due to TCA cycle activity and activity of glutamate-oxalaocetate transaminase. No label is incorporated into alanine (pyruvate). Some incorporation into aspartate if glucose is in the perfusion medium. 

The reversible transfer of an amino group from an amino acid to a keto acid was first described by Braunstein and Riitsman/ who named this type of enzyme aminopherase. This term has been superseded by the generally accepted transaminase. Early work established the existence in heart muscle of two transaminases, catalyzing the reactions shown in (I). Claims for a third enzyme, an aspartic-alanine transaminase, were... 

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