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Glucose modulation of glucokinase activation by small molecules
Author(s) -
Ralph Erik C.,
Thomson Jim,
Almaden Jonathan,
Sun Shaoxian
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.334
Subject(s) - glucokinase , allosteric regulation , chemistry , small molecule , enzyme , activator (genetics) , enzyme activator , enzyme kinetics , non competitive inhibition , biophysics , biochemistry , molecule , active site , receptor , biology , organic chemistry
Small molecule activators of glucokinase (GK) were used in kinetic and equilibrium binding studies to probe the biochemical basis for their allosteric effects. These small molecules decreased the glucose K 0.5 (∼1 mM vs. ∼8 mM) and the Hill coefficient (1.2 vs. 1.7), and lowered the k cat to 62%–95% of the control activity. They relieved GK's inhibition from GKRP in a glucose‐dependent manner and exhibited a competitive relationship with respect to GKRP. The intrinsic glucose affinity to the activator‐bound enzyme demonstrated a 700‐fold increase relative to the apo‐enzyme. This is consistent with a reduction in apparent glucose K D and the steady‐state parameter K 0.5 as a result of enzyme equilibrium shifting to the activator‐bound form. The binding of small molecules to GK was dependent on glucose, consistent with the structural evidence for an allosteric binding site which is present in the glucose‐induced, active‐enzyme form of GK, and absent in the inactive apo‐enzyme. A mechanistic model that brings together the kinetic and structural data is proposed which allows qualitative and quantitative analysis of the glucose‐dependent GK regulation by small molecules. The regulation of GK activation by glucose may have an important implication for the discovery and design of GK activators as potential antidiabetic agents. Support was provided by the Pfizer La Jolla Postdoctoral Program.