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  • Title: Channeling behavior and activity models for Escherichia coli K-12 acetohydroxy acid synthases at physiological substrate levels.
    Author: Herring PA, McKnight BL, Jackson JH.
    Journal: Biochem Biophys Res Commun; 1995 Feb 06; 207(1):48-54. PubMed ID: 7857304.
    Abstract:
    The channeling behavior of acetohydroxy acid synthases I and III (EC 4.1.3.18; AHAS) was studied by computer simulation of activities over a wide range of concentrations for the substrates pyruvate and 2-ketobutyrate. The ratios of reaction rates for both channels and three-dimensional plots of single-channel reaction rates versus substrate concentrations were introduced to compare the substrate channeling properties of the isozymes. Substrate ranges were identified in which AHAS I and III operated both channels, and in which they used only one. Kinetic constants were varied to simulate whether and how AHAS might be made channel-specific. Our study suggests that AHAS might be made channel-specific for acetolactate but not for acetohydroxybutyrate. We postulate specific physiological roles for AHAS I and III to support cell growth under conditions that vary the levels and balance of substrates.
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