EN
The four-membered cycle of enzymatic reactions with repression of enzyme synthesis in the presence of cyclic symmetry is presented. Experimental premises, formulation of the model, analytical analysis, bifurcations diagrams and numerical solutions are shown. By Hopf bifurcation theory, the conditions of oscillations were found for two kinds of the model: fully symmetric and extended one. The latter of them reconstructs better the experimental results than the former one. The models are more general and can be related to rings of coupled biological oscillators.