I did some basic online research on digestive enzymes, metabolic enzymes, and metabolism in general and I posted the info in my blog http://mpdela.blogspot.com/2008/09/digestive-and-metabolic-enzymes_1414.html to help us put things into perspective. Digestive enzymes are important to help us breakdown foods so the nutrients can go through the semi-permeable wall of the intestines into the bloodstream. Metabolic enzymes are the biomolecules that catalyze (i.e. increase the rates of) chemical reactions that are carried out by a cell to break down large molecules to provide the energy required to maintain the internal composition of the cell and support its function, and to use energy to construct components of cells. Although these are both enzymes, they have specific functions. A deficiency of one enzyme cannot be compensated by another enzyme.
Hope this post is helpful in understanding what enzymes are all about.