Open AccessSteady‐state kinetics of skeletal muscle myosin light chain kinase indicate a strong down regulation by products
Author(s) -
GEUSS Ursula,
MAYR Georg W.,
HEILMEYER Ludwig M. G.
Publication year - 1985
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1985.tb09305.x
Subject(s) - myosin light chain kinase , chemistry , immunoglobulin light chain , myosin , kinetics , stereochemistry , enzyme , equilibrium constant , skeletal muscle , steady state (chemistry) , product inhibition , reversible reaction , biophysics , chain (unit) , biochemistry , non competitive inhibition , catalysis , biology , physics , quantum mechanics , antibody , immunology , astronomy , endocrinology
The kinetic behaviour of myosin light chain kinase isolated from skeletal muscle was studied under steadystate conditions using highly purified phosphorylatable light chains 2 (LC2). Forward reaction, product inhibition, and reverse reaction data indicate a sequential mechanism which can be interpreted best by a rapid‐equilibrium random bi‐bi reaction model. The forward reaction parameters are K ATP = 150 μM, K LC2 = 5.3 μM, and K i , LC2 = 7.6 μM. The enzyme forms a dead‐end complex with ADP and light chain 2; K d , ADP of this complex is 50 μM. The forward reaction is also strongly inhibited by the phosphorylated light chain 2, K i , LC2P is 1.5 μM. An equilibrium constant K eq of about 70 can be calculated from the kinetic parameters which agrees with the directly measured value of about 60. The role of the two inhibitory mechanisms in the regulation of the enzyme and of the high energy of the light chain phosphate bond as deducible from K eq are discussed.