The interaction between some serine proteinases and horse leucocyte inhibitor.

The research study explores how horse blood leucocyte cytosol, a biological inhibitor, interacts with various serine proteinases. Their findings reveal that this inhibitor is particularly effective against elastases.

Objective and Methods

• The objective of this study was to investigate the interaction between serine proteinases, which are enzymes that can break down proteins, and a purified inhibitor derived from horse leucocyte cytosol, which is a component of white blood cells.
• The researchers subjected this inhibitor to a range of enzymes, including trypsin, chymotrypsin, elastases and a serine proteinase from S. aureus, a bacteria, to observe how they interact over variable timeframes.
• They then analyzed the resulting products using gradient polyacrylamide gel electrophoresis, which is a method to separate proteins on the basis of their size, in the presence of a compound called sodium dodecyl sulphate.
• The researchers also calculated molar ratios, association rate constants, and inhibition constants to further understand this interaction.

Key Findings

• The study found that elastases (a type of serine proteinase) form stable complexes with the inhibitor at less than 10(-10) M, indicating a high potency of inhibition, and does not break down even after 30 minutes of exposure at 20 degrees Celsius.
• The reactions happened extremely fast, completing within one second, which is significantly faster than similar reactions with other enzymes such as chymotrypsin and trypsin.
• Interestingly, the serine proteinase from S. aureus did not react or deactivate the inhibitor.
• On the contrary, the inhibitor’s complexes with trypsin and chymotrypsin underwent digestion even at a molar ratio of 2:1.
• All these observations led the researchers to conclude that the horse leucocyte cytosol inhibitor is a specific and highly effective inhibitor against elastases.