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Dipeptidyl peptidases in human muscle disease
Summary
Researchers identified four dipeptyl peptidases in human muscle, with elevated levels of dipeptyl peptidases I and II in muscular dystrophy and polymyositis patients. Dipeptyl peptidase IV also increased in various muscle wasting conditions.
Area of Science:
- Biochemistry
- Enzymology
- Muscle Physiology
Background:
- Four distinct dipeptyl peptidases (I, II, III, and IV) were identified in human muscle homogenates.
- These enzymes selectively hydrolyze specific beta-naphthylamide substrates.
- Their enzymatic properties, including optimal pH and cation sensitivity, were characterized.
Purpose of the Study:
- To investigate the activity and levels of dipeptyl peptidases in human muscle.
- To determine if dipeptyl peptidase levels are altered in neuromuscular diseases.
- To explore the potential origins of altered enzyme activity in diseased muscle.
Main Methods:
- Selective inhibitors of arylamidase were used to distinguish the four dipeptyl peptidases.
- Enzyme activity was measured at different pH values.
- Dipeptyl peptidase levels were compared between healthy controls and patients with muscular dystrophies, polymyositis, and other muscle wasting conditions.
Main Results:
- Dipeptidyl peptidase I (DPP I) and II (DPP II) showed increased activity in muscular dystrophies and polymyositis.
- Dipeptyl peptidase III (DPP III) levels remained unchanged in the examined neuromuscular diseases.
- Dipeptyl peptidase IV (DPP IV) exhibited a marked increase across various muscle wasting conditions.
Conclusions:
- Elevated DPP I and DPP II in muscle diseases may be linked to lysosomal activation during degeneration.
- The significant increase in DPP IV suggests contributions from non-lysosomal sources, potentially microsomal membranes, in diseased muscles.
- Serum levels of DPP II and DPP IV were not altered in Duchenne dystrophy patients.