Cysteine and metalloproteinase activities in serum of Duchenne muscular dystrophic genotypes.

Lysosomal cysteine proteinase (cathepsin B, H, and L) and MMP-7ase muscle metalloproteinase activities were measured in serum from Duchenne muscular dystrophic male patients and their mothers as gene-carriers. The activity of cathepsin H significantly increased in the Duchenne muscular dystrophic (DMD)-hemizygotes group and in the group of DMD heterozygotes. Significant positive correlation was found between the activity of serum creatine kinase (which previously has been proven to be a marker of muscular dystrophy) and of cathepsin L in the DMD-hemizygotes group. Furthermore, correlations were found between the activity of creatine kinase and MMP-7ase or between activity of creatine kinase and cathepsin H in the DMD heterozygotes. The changes in activity of proteolytic enzymes in serum of dystrophic patients can be explained by the elevated proteolytic enzyme activity in dystrophic muscle observed previously.