The present invention relates to conjugates of a lipid, substrate peptide of an enzyme secreted from the cells of mammals, including humans, and a water-soluble polymer that can be used as colloidal carriers and the like of tissue-specific drug delivery systems, methods of producing these conjugates, peptide-water-soluble polymer conjugates optionally having protective groups that are useful as the intermediates of these conjugates, colloidal carriers made from these conjugates, and tissue-specific drug delivery systems that use these colloidal carriers.