Abstract: The invention provides a cell control product for use with a cytoenzymology assay to confirm enzymatic activity in devices employing electronic and/or optical means. The cell control product comprises a lyophilized mammalian cell which is capable of being rehydrated in water to exhibit cellular structure and cellular enzymatic activity so that said lyophilized cells can function effectively as a cytoenzymology cell control in an enzymatic analysis. The cellular structure of the cell control is capable of being authenticated by light scatter or microscopy analysis and the cellular enzymatic activity is capable of being authenticated by fluorescence analysis. The cell control exhibits a real time stability when stored at between 2 and 8.degree. C. for at least a two month period of time. Preferably the mammalian cell is an abnormal cell selected from Molt 4, CCRF-CEM and HL-60 cell lines.

Abstract: A two-reagent assay system for determination of gamma glutamyl transpeptidase enzyme activity in a biological fluid. Gamma glutamyl-p-nitroanalide substrate for the enzymatic reaction is provided in a first reagent which is a dry mixture of the substrate with a normally solid acid which is water soluble and a second reagent includes a buffer and a component selected for reception of the glutamyl product of the enzymatic reaction.