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Energetics of allosteric control in native and evolved V‐system enzymes.
Author(s) -
Pettigrew Donald Wayne,
Flynn Jesse,
Jurrens Rebecca,
Saxton Brandon
Publication year - 2006
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.20.4.a52-b
Subject(s) - allosteric regulation , allosteric enzyme , chemistry , glycerol kinase , energetics , enzyme , substrate (aquarium) , biochemistry , stereochemistry , biology , ecology
Catalytic activity of E. coli glycerol kinase is inhibited by phosphotransferase system phosphocarrier protein IIA Glc . This allosteric control is transplanted into the IIA Glc ‐naive glycerol kinase from H. influenzae by 11 amino acid changes – 8 form the IIA Glc ‐binding site and 3 couple IIA Glc binding to inhibition. The approach of linked functions is used to compare the native and transplanted allosteric control by determining ATP‐IIA Glc coupling energetics by using steady‐state enzyme kinetics. For both enzymes, weak cooperative coupling between ATP and IIA Glc is observed, and the dominant action of IIA Glc is reduction of V max . The values for coupling activation enthalpy and entropy are: E. coli glycerol kinase; H c ‡ =6.9 kcal/mol, S c ‡ =18 cal/K/mol; H. influenzae glycerol kinase; H c ‡ =2.6 kcal/mol, S c ‡ =7 cal/K/mol. This enthalpy‐entropy compensation for allosteric inhibition of reaction velocity is the same as that observed for allosteric inhibition of substrate binding in other enzymes, suggesting coupling between IIA Glc binding and binding of the substrate/product species in the rate‐determining step. The similar coupling energetics suggests that the molecular basis of the control is the same for both the native and transplanted allosteric control and is thus likely related to the active site closure motions that are characteristic of the sugar kinase superfamily. (Supported by NIH grant GM68768)