Asparagine transaminase from rat liver.

Area of Science:

• Biochemistry
• Enzymology

Background:

• Asparagine transaminase is an enzyme involved in amino acid metabolism.
• Understanding its substrate specificity is crucial for metabolic pathway analysis.

Purpose of the Study:

• To purify and characterize asparagine transaminase from rat liver.
• To determine the enzyme's substrate specificity for amino acids and alpha-keto acids.
• To elucidate the kinetic mechanism of the enzyme.

Main Methods:

• Purification of asparagine transaminase from rat liver (approx. 200-fold).
• Enzyme activity assays with various amino acid and alpha-keto acid substrates.
• Kinetic analysis of the asparagine glyoxylate transamination reaction.

Main Results:

• The purified enzyme exhibited broad substrate specificity, accepting amino acids like asparagine, S-methylcysteine, phenylalanine, and aspartate.
• The enzyme also utilized alpha-keto acids such as glyoxylate, pyruvate, and phenylpyruvate.
• Substrates with a beta-carbon branch point were inactive.
• Kinetic data supported a ping-pong mechanism for the asparagine glyoxylate transamination.

Conclusions:

• Asparagine transaminase from rat liver possesses a broad substrate range.
• The enzyme's activity is dependent on the structure of the amino and alpha-keto acid substrates.
• A ping-pong mechanism governs the transamination reaction catalyzed by this enzyme.