Active Ca2+/calmodulin (CaM)-dependent myosin light chain kinase (MLCK) plays an important role in the process of MLC phosphorylation and consecutive smooth muscle contraction. Here, we propose a mathematical model of a detailed kinetic scheme describing interactions among Ca2+, CaM and MLCK and taking into account eight different aggregates. The main model result is the prediction of the Ca2+ dependent active form of MLCK, which is in the model taken as proportional to the concentration of Ca4CaM (.) MLCK complex. Wegscheider's condition is additionally applied as a constraint enabling the prediction of some parameter values that have not yet been obtained by experiments. (c) 2005 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.