In vitro analysis of the chain termination reaction in the synthesis of poly-(R)-beta-hydroxybutyrate by the class III synthase from Allochromatium vinosum.
Biomacromolecules
; 6(4): 2113-9, 2005.
Article
em En
| MEDLINE
| ID: mdl-16004452
ABSTRACT
Allochromatium vinosum polyhydroxyalkanoate synthase catalyzes formation of poly-(R)-3-hydroxybutyrate (PHB) from (R)-3-hydroxybutyryl-coenzyme A (HB-CoA). (R)-3-Hydroxybutyryl-N-acetylcysteamine (HB-NAC) is an alternative substrate for this synthase in vitro, with a turnover 1% that of HB-CoA. With HB-NAC, the molecular weight (M(w)) of PHB produced at substrate-to-enzyme ratios of 1500-15 000 is approximately 75 kDa. (1)H NMR shows that PHB produced has hydroxybutyrate at the alcohol end and N-acetylcysteamine (NAC) at the carboxylate end of the polymer. Exogenous NAC has no effect on the M(w) of PHB produced with HB-CoA or HB-NAC in vitro, whereas PHB from a polymerization reaction with both HB-CoA and HB-NAC has intermediate M(w). These results can be accommodated by two models. In the first, NAC liberated at the active site during polymerization acts as a chain transfer agent. In the second, there is a noncovalent polymer intermediate covalently linked to NAC, which can dissociate from the active site.
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Coleções:
01-internacional
Contexto em Saúde:
3_ND
Base de dados:
MEDLINE
Assunto principal:
Poliésteres
/
Aciltransferases
/
Chromatiaceae
/
Hidroxibutiratos
Idioma:
En
Revista:
Biomacromolecules
Ano de publicação:
2005
Tipo de documento:
Article