PMID:9555876

Citation	Slater, S, Houmiel, KL, Tran, M, Mitsky, TA, Taylor, NB, Padgette, SR and Gruys, KJ (1998) Multiple beta-ketothiolases mediate poly(beta-hydroxyalkanoate) copolymer synthesis in Ralstonia eutropha. J. Bacteriol. 180:1979-87
Abstract	Polyhydroxyalkanoates (PHAs) are a class of carbon and energy storage polymers produced by numerous bacteria in response to environmental limitation. The type of polymer produced depends on the carbon sources available, the flexibility of the organism's intermediary metabolism, and the substrate specificity of the PHA biosynthetic enzymes. Ralstonia eutropha produces both the homopolymer poly-beta-hydroxybutyrate (PHB) and, when provided with the appropriate substrate, the copolymer poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV). A required step in production of the hydroxyvalerate moiety of PHBV is the condensation of acetyl coenzyme A (acetyl-CoA) and propionyl-CoA to form beta-ketovaleryl-CoA. This activity has generally been attributed to the beta-ketothiolase encoded by R. eutropha phbA. However, we have determined that PhbA does not significantly contribute to catalyzing this condensation reaction. Here we report the cloning and genetic analysis of bktB, which encodes a beta-ketothiolase from R. eutropha that is capable of forming beta-ketovaleryl-CoA. Genetic analyses determined that BktB is the primary condensation enzyme leading to production of beta-hydroxyvalerate derived from propionyl-CoA. We also report an additional beta-ketothiolase, designated BktC, that probably serves as a secondary route toward beta-hydroxyvalerate production.
Links	PubMed PMC107120
Keywords	Acetyl-CoA C-Acyltransferase/genetics; Acetyl-CoA C-Acyltransferase/isolation & purification; Acetyl-CoA C-Acyltransferase/metabolism; Alcaligenes/enzymology; Alcaligenes/genetics; Amino Acid Sequence; Base Sequence; Genes, Bacterial; Genetic Complementation Test; Genotype; Kinetics; Molecular Sequence Data; Plasmids; Polymers/metabolism; Recombinant Proteins/isolation & purification; Recombinant Proteins/metabolism; Sequence Alignment; Sequence Homology, Amino Acid; Substrate Specificity
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
CUPNH:Q0KBP1		GO:0008415: acyltransferase activity	ECO:0000314:		F		Beta-ketothiolase capable of producing medium chain-length 3-ketoacyl-CoA. Involved in polyhydroxyalkanoate biosynthesis. See Table 3 in Slater et al., 1998.	complete

References

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