Nutrition, lysosomal proteases, and protein breakdown.

We review the role played by the lysosomal proteases on cellular protein breakdown and their relation to nutrition research. Several recent works have shown that an important group of lysosomal proteases (cathepsins) are directly responsible for the maintenance of protein breakdown. The determination of their enzyme activity or measurement of mRNAs as an index of gene expression have provided new views about the mechanisms of protein-breakdown regulation. The introduction of molecular biology could provide new ways with which to manipulate the catabolic response of injured patients.