Neutral proteinases in muscle tissue and cells

Area of Science:

• Biochemistry
• Proteomics
• Enzymology

Background:

• Skeletal muscle contains various proteinases that play roles in tissue remodeling and function.
• Chymase is a serine protease known to be present in mammalian tissues, but its specific roles and counterparts in skeletal muscle are not fully elucidated.

Purpose of the Study:

• To isolate and characterize chymase from rat skeletal muscle.
• To compare chymase with other proteinases in rat muscle that hydrolyze chymase substrates.
• To identify and partially characterize other distinct proteinases present in rat skeletal muscle.

Main Methods:

• Rat hind limb skeletal muscles were homogenized in a phosphate buffer containing NaCl.
• Enzymes were purified from the 100,000 x g supernatant of the muscle homogenate.
• Proteinase activity against chymase substrates was assessed.
• Partial characterization of isolated metalloproteinase (MMP-7-ase) and serine proteinase (ATN-ase) was performed.

Main Results:

• Chymase was successfully isolated from rat skeletal muscle tissue.
• Other proteinases that hydrolyze chymase substrates were detected in the muscle extract.
• A metalloproteinase, designated MMP-7-ase, was partially purified and characterized.
• A serine proteinase, designated ATN-ase, was also partially purified and characterized.
• Both MMP-7-ase and ATN-ase were demonstrated to be distinct from chymase.

Conclusions:

• Rat skeletal muscle contains multiple proteinases capable of hydrolyzing chymase substrates.
• Chymase is present in rat skeletal muscle, alongside other distinct metalloproteinase and serine proteinase activities.
• The identified MMP-7-ase and ATN-ase represent novel or less-characterized proteinases in skeletal muscle, distinct from chymase.