For an enzymatic reaction the rate constants in the assumed mechanism (k(1), k(-1), etc.) sometimes can be calculated from the steady-state parameter values (V-max, K-m, etc.) and sometimes cannot. When identifiability problems occur, these are obscured by redundancy occurring among the steady-state parameters. This redundancy is only partly revealed by the known Haldane relations. We found the additional constraints between the parameters. These relations allow to predict in which situation rate constants are identifiable by steady-state kinetic methods.