Transaminase

A BRIEF STUDY

1. TRANSAMINASE

2. Transaminase  or an  aminotransferase  is an  enzyme  that  catalyzes  a type of reaction between an  amino acid  and an  α- keto acid . They are important in the synthesis of amino acids, which form proteins. DEFINITION

3. An amino acid contains an  amine  (NH 2 ) group. A keto acid contains a  keto  (=O) group. In  transamination , the NH 2  group on one molecule is exchanged with the =O group on the other molecule. The amino acid becomes a keto acid, and the keto acid becomes an amino acid

4. The transaminase enzymes are important in the production of various amino acids, and measuring the  concentrations  of various transaminases in the blood is important in the diagnosing and tracking many  diseases .

5. Aspartate aminotransferase (EC 2.6.1.1; l-aspartate:2-oxoglutarate aminotransferase ; AST) and alanine aminotransferase (EC 2.6.1.2; l-alanine:2- oxoglutarate aminotransferase ; ALT) are examples of aminotransferases that are of clinical interest.

6. Transaminases require the coenzyme  pyridoxal -phosphate , which is converted into  pyridoxamine  in the first phase of the reaction, when an amino acid is converted into a keto acid. Enzyme-bound  pyridoxamine  in turn reacts with  pyruvate ,  oxaloacetate , or  alpha- ketoglutarate , giving  alanine ,  aspartic acid , or  glutamic acid , respectively. Many transamination reactions occur in tissues, catalysed by transaminases specific for a particular amino/ keto acid pair. The reactions are readily reversible, the direction being determined by which of the reactants are in excess

7. Transaminases are widely distributed throughout the body. AST is found primarily in the heart, liver, skeletal muscle, and kidney, whereas ALT is found primarily in the liver and kidney, with lesser amounts in heart and skeletal muscle. ALT is exclusively cytoplasmic ; both mitochondrial and cytoplasmic forms of AST are found in cells. These are genetically distinct isoenzymes with a dimeric structure composed of two identical polypeptide subunits of about 400 amino acid residues .

8. Transaminase Activities in Human Tissues, Relative to Serum as Unity AST ALT Heart 7800 450 Liver 7100 2850 Skeletal muscle 5000 300 Kidneys 4500 1200 Pancreas 1400 130 Spleen 700 80 Lungs 500 45 Erythrocytes 15 7 Serum 1 1

9. PURPOSE OF EXAMINATION Alanine amino transferase (glutamate pyruvate transaminase ) belongs to the group of transaminase , which catalyses the conversion of amino acids to the corresponding alpha keto acids via the transfer of amino groups, they also catalyse the reverse process. Estimation of alanine aminotransferase helps in the diagnosis of MI, hepatopathies , muscular dystrophy, and damage to the internal organs. ALT (ALANINE AMINO TRANSFERASE)

10. METHODS BASED ON IFCC RECOMMENDATION ALT transfers the amino group from alanine to 2-oxoglutarate to form pyruvate and glutamate. The addition of pyridoxal phisphate to the reaction mixture ensures maximum catalytic activity of ALT. The pyruvate enters a lactate dehydrogenase (LDH) catalysed reaction with NADH to produce lactate and NAD + . The decreased in absorbance due to consumption of NADH is measured at 340 nm and is proportional to the ALT activity in the sample. Endogenous pyruvate is removed during incubation period. PRINCIPLE OF THE PROCEDUER USED FOR EXAMINATION

11. 2- OXOGLUTARATE + L-ALANINE L-GLUTAMATE + PYRUVATE PYRUVATE + NADH + H+ L- LACTATE + NAD + REACTION PRINCIPLE

12. Male (adult) - <50 U/L Female (adult) - < 35 U/L Newborn/ infants - 13 – 45U/L BIOLOGICAL REFERENCE INTERVALS

13. PURPOSE OF EXAMINATION Ast occurs in a wide variety of tissues including liver, cardiac muscle, skeletal muscle, brain, kidneys, lungs pancreas, erythrocytes and leucocytes with highest activities found in liver and skeletal muscle. Measurment of AST is indicated in the diagnosis , differentiation and monitoring of hepatobilliary disease, myocardial infarction and skeletal muscle. AST(ASPARATE AMINOTRANSFERASE)

14. TEST PRINCIPLE Method based on the recommendation of the “international federation for clinical chemistry”(IFCC) In this method, Asparate aminotransferase (AST) catalyses the transamination of aspartate and 2- oxoglutarate , forming l-glutamate and oxalacetate . The addition of pyridoxal phosphate to the reaction mixture ensures maximum catalytic activity of AST. PRINCIPLE OF THE PROCEDURE USED FOR EXAMINATION

15. The oxaloacetate is reduced to L- malate by malate dehydrogenase (MDH), while NADH is simultaneously converted to NAD + . The decrease in absorbance due to the consumption of NADH is measured at 340nm and is proportional to the AST activity in the sample. Endogenous pyruvate is removed by the LDH-reaction during the incubation period.

16. ADULT - <35 U/L NEWBORN - 25 - 75 U/L INFANT - 15 - 60 U/L BIOLOGICAL REFERANCE INTERVALS

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