The Expert Panel of Enzymes, International Federation of Clinical Chemistry has published its recommendations for the measurement of serum AST. The Synermed® method for measuring AST activity in serum is based upon these recommendations.
The aspartate aminotransferase in the sample catalyzes the transfer of the amino group from aspartate to alpha-ketoglutarate to form oxalacetate and glutamate.
L-aspartate + α-ketoglutarate -> oxalacetate + glutamate
The oxalacetate is reduced to malate in the presence of malate dehydrogenase (MDH) with the concurrent oxidation of reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide [NAD].
oxalacetate + NADH -> malate + NAD
The resulting rate of decrease in absorbance at 340 nm is directly proportional to the AST activity in the sample. The enzyme lactate dehydrogenase [LDH] is included in the reagent to prevent interference from endogenous alpha-keto acids normally found in human serum.