Covalently bound pyruvate in phosphopantothenoylcysteine decarboxylase from horse liver.

This research article explores how the enzyme found in horse livers called phosphopantothenoylcysteine decarboxylase (EC 4.1.1.36) binds with pyruvate through a chemical process. The findings reveal that pyruvate, a key component in metabolism, plays an important role in the catalytic activity of this particular enzyme, adding to the understanding of mammalian enzymes and their functions.

Experiment Procedure and Findings

• The enzyme phosphopantothenoylcysteine decarboxylase found in horse livers incorporates non-exchangeable tritium, a radioactive isotope of hydrogen, extracted from borotritide. This incorporation results in a decrease in the enzyme’s activity.
• The researchers found that the presence of substrate—any substance on which an enzyme acts—hinders both the incorporation of tritium into the enzyme and the subsequent decrease in activity.
• They then exposed the protein with the incorporated tritium to acid and base hydrolysis. Hydrolysis is a chemical breakdown due to reaction with water. This process releases a substance called lactate, which the researchers identified through several testing methods including high-voltage paper electrophoresis, paper chromatography, and silicic acid chromatography.

Significance of Pyruvate Involvement

• The results from the hydrolysis and testing revealed that the enzyme has pyruvate covalently bound to it through an ester linkage. An ester linkage is a type of covalent bond that forms between a carboxyl group and a hydroxyl group. In this case, the bond is between pyruvate and the phosphopantothenoylcysteine decarboxylase enzyme.
• The presence of this bound pyruvate implies its direct involvement in the enzyme’s catalytic activity. The catalytic activity of an enzyme refers to its ability to increase the rate of a specific biochemical reaction.
• Therefore, the study provides yet another example of an enzyme in mammals where pyruvate is directly involved in its catalytic activity, expanding existing knowledge on the diverse applications and functions of pyruvate in biochemical processes.