The importance of PHB-synthase substrate specificity in polyhydroxyalkanoate synthesis by Alcaligenes eutrophus

1 January 1989

journal article
Published by Oxford University Press (OUP) in FEMS Microbiology Letters

Vol. 57 (1) , 1-6
https://doi.org/10.1016/0378-1097(89)90136-5

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.

Keywords

This publication has 0 references indexed in Scilit: