Human cathepsin G. Catalytic and immunological properties

Area of Science:

• Biochemistry
• Enzymology
• Immunology

Background:

• Cathepsin G is a neutral proteinase found in human spleen.
• Its enzymatic properties and comparison to other proteases require detailed investigation.

Purpose of the Study:

• To characterize the specificity and kinetic properties of human cathepsin G.
• To investigate the sensitivity of cathepsin G to inhibitors.
• To confirm the immunological identity of cathepsin G with neutrophil granulocyte enzymes.

Main Methods:

• Enzyme kinetics using low-molecular-weight substrates.
• pH activity profiling.
• Inhibitor sensitivity assays comparing cathepsin G, chymotrypsin, and subtilisin.
• Immunological characterization using rabbit anti-(human cathepsin G) serum and agarose gel electrophoresis.

Main Results:

• Cathepsin G hydrolyzes substrates similarly to chymotrypsin but with distinct kinetic constants.
• Optimal activity for cathepsin G occurs between pH 7.5-8.0.
• Cathepsin G exhibits serine proteinase characteristics but is less inhibited by tosylphenylalanine chloromethyl ketone than chymotrypsin.
• Immunological assays demonstrate cathepsin G is identical to the chymotrypsin-like enzyme in neutrophil azurophil granules.

Conclusions:

• Cathepsin G is a serine proteinase with specific hydrolytic activity.
• Its immunological identity with neutrophil enzymes highlights its role in innate immunity.
• Understanding cathepsin G's properties aids in developing targeted therapeutic strategies.