Isoenzymes (or isozymes) are proteins which catalyze the same chemical reaction but differ in their molecular structure and between species. These enzymes can be separated using chromatography or electrophoresis, resulting in a species-specific zymogram. A comparison of the mobility of isoenzymes from cell lines derived from different species can be used to detect inter-species cross-contamination if the contaminating cells represent at least 10% of the total cell population.
In most cases, the analysis of four different isoenzymes (nucleoside phosphorylase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, lactate dehydrogenase) is sufficient to confirm the identity of the sample of interest . Only the differentiation of mouse and hamster cell lines requires the additional analysis of peptidase B. In general, isoenzyme profiling is suggested as a rapid and easily conducted technique to check for inter-species cross-contamination. It can be performed with a commercially available kit designed to confirm authentication by determination of the mobility of seven isozymes for six cell lines in less than three hours .
1. Nims et al. (1998) Sensitivity of isoenzyme analysis for the detection of interspecies cell line cross-contamination. In vitro Cell Dev Biol Anim. 34: 35-39.
2. Hay et al. (2000) Cell line preservation and characterization. In Masters, J.R.W (ed) Animal cell culture, a practical approach. Oxford, U.K., IRL Press at Oxford University Press. 95-148.