Open AccessThe importance of PHB‐synthase substrate specificity in polyhydroxyalkanoate synthesis by Alcaligenes eutrophus
Author(s) -
Haywood G.W.,
Anderson A.J.,
Dawes E.A.
Publication year - 1989
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1989.tb03210.x
Subject(s) - polyhydroxyalkanoates , atp synthase , polyhydroxybutyrate , alcaligenes , granule (geology) , biochemistry , chemistry , carbon source , bacteria , stereochemistry , enzyme , biology , pseudomonas , paleontology , genetics
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 (C 4 –C 10 ). 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 C 4 and C 5 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.