Fluorochrome-labelled Lysozyme : Reagent for the Detection of Lysozyme Substrate in Cells

Abstract

THE lytic enzyme lysozyme has been shown to become specifically absorbed on to its mucopeptide substrate in bacterial cell walls¹. We have attempted to make use of this specific absorption by labelling lysozyme with a fluorescent dye. By this means we have been able to detect lysozyme-sensitive mucopeptide in bacterial cells with the fluorescence microscope. Such tracing of proteins by means of labelling with fluorescent dyes has been a successful technique in recent years, particularly in examining antibody-antigen reactions², and has been used to follow the fate of labelled lipase added to growing tissue cultures³. The successful use of fluorochrome-labelled lysozyme in this fashion seemed possible because, although low concentrations of the enzyme lyse sensitive cells, high concentrations do not, and may even raise the optical density of suspensions of bacteria^4,5. This auto-inhibition of lysozyme action at high enzyme concentrations probably occurs because the enzyme molecules sterically hinder their own action.