Glutamic pyruvic enzyme

Recently we have evaluated several exogenous and endogenous tests of liver function in rainbow trout following intoxication by the model hepatotoxicant CCl. The results of these studies indicate that elevated plasma activity of the enzyme glutamate-pyruvate transaminase (GPT) is the most sensitive endogenous index of... 

This enzyme [EC 2.6.1.2], also known as glutamic-pyruvic transaminase and glutamic-alanine transaminase, catalyzes the pyridoxal-phosphate-dependent reaction of alanine with 2-ketoglutarate, resulting on the production of pyruvate and glutamate. 2-Aminobutanoate will also react, albeit slowly. There is another alanine aminotransferase [EC 2.6.1.12], better known as alanine-oxo-acid aminotransferase, which catalyzes the pyridoxal-phosphate-dependent reaction of alanine and a 2-keto acid to generate pyruvate and an amino acid. See also Alanine Glyoxylate Aminotransferase... 

This enzyme [EC 2.6.1.21], also known as D-aspartate aminotransferase, D-amino acid aminotransferase, and D-amino acid transaminase, catalyzes the reversible pyridoxal-phosphate-dependent reaction of D-alanine with a-ketoglutarate to yield pyruvate and D-glutamate. The enzyme will also utilize as substrates the D-stereoisomers of leucine, aspartate, glutamate, aminobutyrate, norva-hne, and asparagine. See o-Amino Acid Aminotransferase... 

The normal proton abstraction which precedes 3-elimination induces allene formation from II. The allene, being a Michael acceptor then inactivates the enzyme via an alkylative process involving a nucleophilic (Nu) residue on the enzyme. Propargylglycine has since been shown to also irreversibly inactivate glutamate-pyruvate transaminase (8). 

Figure 3. Schematic representation of five enzyme activity levels in blood serum as a result of various liver diseases. These data (28) do not show the large range in values among individuals. GOT, glutamate-oxaloacetate transaminase GPT, glutamate-pyruvate transaminase GlDH, glutamate dehydrogenase LDH, lactate dehydrogenase P, alkaline phosphatase.

E-7) SGPT (serum glutamate pyruvate transaminase), more recently called ALT (alanine aminotransferase), acts at diis step. Both names make sense, depending on which way you read the chemical reaction. This enzyme is especially concentrated in the liver it leaks out of the liver cell and rises in the serum with liver damage, as in hepatitis and mononucleosis. It does not significantly increase in myocardial infarction and, hence, the test is more specific than SGOT for liver disease. 

Transaminases The transaminases catalyze the reversible transformation of a-ketoacids into amino acids. Most frequently, the 2 transaminases GPT (= glutamic pyruvic transaminase) (or ALT = alamine transaminase) and GOT (= glutamic oxaloacetic transaminase) (or AST = aspartate transaminase) are used for enzyme diagnostics (F. DeRitis et at., 1955 F. Wroblewski et al., 1955). (s. tab. 5.4) While GOT is distributed evenly, the GPT concentration continuously decreases from periportal to pericentral in the acinus. These are considered to be the basic parameters in the diagnosis and follow-up of hepatocellular disease. If the cause of elevated transaminases remains unclear, the indication for liver biopsy is given. (28, 30, 31, 34)... 

The pyruvate carboxylase reaction is activated by Mg + and, through mass action, by an increase in either the [ATP]/[ADP] or the [pyruvate]/[oxaloacetate] ratio. It is virtually inactive in the absence of acetyl-CoA, an allosteric activator. The enzyme is allosteiically inhibited by glutamate, since oxaloacetate formed in excess would flood the TCA cycle and result in a buildup of a-ketoglutarate and glutamate. Pyruvate carboxylase... 

The equilibrium of these reactions lies almost completely on the side of lactate. However, by trapping the pyruvate in a subsequent reaction catalyzed by the enzyme glutamate-pyruvate transaminase (GPT) in the presence of L-glutamate, the equilibrium can be displaced in favour of pyruvate and NADH (eqn. 2). 

The enzyme catalyzing the reversible transamination of alanine and a-ketoglutarate is alanine aminotransferase (ALT), and isoenzymes occur in both the cytosol and mitochondria. This enzyme occurs in many tissues and is particularly active in the liver. An increase of this enzyme in the serum (sometimes referred to as SGPT, serum glutamic pyruvic transaminase) is indicative of hepatic damage. 

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