Particular Changes in the Activity of Intramuscular Dipeptidyl Peptidase III in Comparison to Those of Other Hydrolytic Enzymes in Dystrophic Mice

Abstract

Muscular dystrophy is known to occur mainly in hindlimb muscle, rather than in forelimb muscle, of dystrophic mice. In order to explain this phenomenon, we measured the activities of 12 hydrolytic enzymes, including exopeptidases, endopeptidases, and glycosidases, in muscle of forelimb and hindlimb. In spite of similar enzymatic changes in both limbs, multivariate analysis enabled us to extract two important factors that may explain the difference in the metabolism between forelimb muscle and hindlimb muscle of dystrophic mice. Of the two factors, one was closely correlated to mannosidase, DPP-IV, PEP, and cathepsin B, while the other was correlated to DPP-III, kallikrein, and AP-A. Of these enzymes, DPP-III was particular in that its activity was decreased in forelimb, but not in the hindlimb, muscle of dystrophic mice. The lack of a significant decrease in this enzymatic activity may prompt the muscular breakdown in the hindlimb of dystrophic mice.