Preparation of water-soluble high-molecular weight substrates for beta-D-galactosidase

Two types of high-molecular water-soluble substrates of beta-D-galactosidase were prepared. Substrate I contains beta-D-[3H]-galactopyranosyl moieties linked, through a hydrocarbon bridge, to a polymeric dialdehyde (oxidized starch) backbone (molecular weight 6,000); in substrate II the backbone is poly-L-lysine (molecular weight 80,000). In the presence of Triton X-100, but not in its absence, D-[3H]-galactose is split from the substrates by homogenates of normal mouse liver or pancreas. It is suggested that substrates I and II could be used to test the integrity of lysosomal and other cellular membranes, and to assess the extent of cellular injury.