Nutritional flexibility of oligotrophic and copiotrophic Antarctic bacteria with respect to organic substrates |
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Authors: | AC Upton DB Nedwell |
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Institution: | Department of Biochemistry, School of Life Sciences, University of Hull, Hull, U.K. |
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Abstract: | Abstract Alcaligenes eutrophus can accumulate poly-3-hydroxybutyrate (PHB) or polyhydroxyalkanoate (PHA) containing only 3-hydroxybutyrate (HB) and 3-hydroxyvalerate (HV) units. Granule-associated PHB-synthase was active with d (?)-3-hydroxybutyryl-CoA and d (?)-3-hydroxyvaleryl-CoA of the range of d (?)- and l (+)-3-hydroxyacyl-CoA substrates tested (C4–C10). In carbon-limited cultures, PHB-synthase was predominantly soluble, becoming granule-associated on transition to nitrogen limitation. Granule-associated PHB-synthase increased in activity at least up to pH 10.0 and K m values of 0.68 mM and 1.63 mM were determined for the C4 and C5 substrates, respectively, at pH 8.5. The soluble PHB-synthase, which was unstable, showed equal activity in the range pH 8.0–10.0, had a K m value for d (?)-3-hydroxybutyryl-CoA of 0.72 mM and an M r of 160,000. PHB does not measurably turn over under steady-state polymer-accumulating conditions. |
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Keywords: | Alcaligenes eutrophus Poly-3-hydrobutate Polyhydroxyalkanoate Synthesis |
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