Lipolytic activity of crude or partially purified lipase of the mouse mammary gland at various substrate concentrations.

The lipolytic activity in crude extracts prepared from mouse mammary glands during lactation and pregnancy or that in extracts partially purified with anion exchange chromatography and ammonium sulfate precipitation depended on the ratio of the extract volume to the substrate amount in the assay emulsion. When the ratio was high, the fatty acid release ceased within a short time of incubation. In this case, the substrate concentration available for the lipase dropped. This decline was considered to occur due to the interaction of the substrate with some substance in the extracts.