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Enzyme Nomenclature
Information on EC 2.3.1.B5 - unclassified polyhydroxybutyrate synthase
Word Map on EC 2.3.1.B5
- 2.3.1.B5
-
polyhydroxyalkanoate
- acetyl-coa
-
alcoholysis
-
polyester
-
low-molecular-weight
- pyruvate
- meliloti
- acetoacetyl-coa
- eutropha
- cap
-
acetoacetyl
-
ralstonia
- cyanobacterium
-
sinorhizobium
- cereus
-
carboxy
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The expected taxonomic range for this enzyme is: Bacteria, Archaea
topEC NUMBER 
COMMENTARY 
2.3.1.B5
preliminary BRENDA-supplied EC number
RECOMMENDED NAME
GeneOntology No.
unclassified polyhydroxybutyrate synthase
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SYSTEMATIC NAME
IUBMB Comments
acyl-CoA:3-hydroxybutyrate O-acyltransferase
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
a PHA-producing strain isolated from a soil sample from western peninsular Malaysia, gene phaCUSMAA2-4
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a PHA-producing strain isolated from a soil sample from western peninsular Malaysia, gene phaCUSMAA2-4
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isolated in Malaysia, gene phbC encoded in the phb operon
UniProt
D2Z0B8 i.e. subunit PhaC, D2Z0B6 i.e. subunit PhaR
D2Z0B8 and D2Z0B6
UniProt
isolated as a PHA producer from the polluted soil in Kitakyushu City, Japan
UniProt
D2Z0B8 i.e. subunit PhaC, D2Z0B6 i.e. subunit PhaR
D2Z0B8 and D2Z0B6
UniProt
isolated as a PHA producer from the polluted soil in Kitakyushu City, Japan
UniProt
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
physiological function
additional information
physiological function
P(3HB) synthase catalyzes polymerization of the 3-hydroxybutyryl-CoA monomers, Pseudomonas sp. USM 4-55 is a soil isolated bacterium that possesses the ability to produce polyhydroxyalkanoates consisting of both poly(3-hydroxybutyrate) homopolymer and medium-chain length monomers (6 to 14 carbon atoms) when sugars or fatty acids are utilized as the sole carbon source
physiological function
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recombinant Escherichia coli expressing PHA synthase from Bacillus cereus shows a reduction of the molecular weight of PHA produced during the stationary phase of growth. Its carboxy end structure is capped by ethanol, as the result of alcoholytic cleavage of PHA chains by PhaRC induced by endogenous ethanol. This scission reaction is also induced by exogenous ethanol in both in vivo and in vitro assays. In addition, PhaRC has alcoholysis activity for PHA chains synthesized by other synthases
physiological function
-
heterologous expression of foreign PHA synthases in the single mutant lacking isoform PhaC2 and in a double mutant lacking both isoforms PhaC1 and PhaC2 results in a significant accumulation of polyhydroxybutanoate in all generated strains. Six of the thirteen generated phaC hybrid vectors lead to an increased polyhydroxybutanoate accumulation in the single mutant in comparison to the wild type strain. All recombinant strains of Rthe double mutant harboring heterologous phaC genes accumulate significantly less polyhydroxybutanoate than the recombinant single mutants and the wild type strain. Recombinant strains with higher content of accumulated polyhydroxybutanoate are linked to higher growth rates and higher maximum ODs, due to the light scattering effect of polyhydroxybutanoate granules. All recombinant strains of the double mutant show significantly decreased growth rates and maximum ODs
physiological function
-
recombinant Escherichia coli expressing PHA synthase from Bacillus cereus shows a reduction of the molecular weight of PHA produced during the stationary phase of growth. Its carboxy end structure is capped by ethanol, as the result of alcoholytic cleavage of PHA chains by PhaRC induced by endogenous ethanol. This scission reaction is also induced by exogenous ethanol in both in vivo and in vitro assays. In addition, PhaRC has alcoholysis activity for PHA chains synthesized by other synthases
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physiological function
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P(3HB) synthase catalyzes polymerization of the 3-hydroxybutyryl-CoA monomers, Pseudomonas sp. USM 4-55 is a soil isolated bacterium that possesses the ability to produce polyhydroxyalkanoates consisting of both poly(3-hydroxybutyrate) homopolymer and medium-chain length monomers (6 to 14 carbon atoms) when sugars or fatty acids are utilized as the sole carbon source
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additional information
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comparison of P(3HB) biosynthesis by recombinant Cupriavidus necator PHB-4 harboring the synthase gene of Cupriavidus sp. USMAA2-4 from various plant oils
additional information
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comparison of P(3HB) biosynthesis by recombinant Cupriavidus necator PHB-4 harboring the synthase gene of Cupriavidus sp. USMAA2-4 from various plant oils
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate](n+1) + CoA
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acylation of C319 causes a shift of the monomeric form of the synthase to its dimeric form, and this shift is accompanied by a substantial increase in its specific activity and a substantial decrease in the lag phase of polymer formation
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-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutyrate](n+1) + CoA
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-
-
-
?
3-hydroxybutyryl-CoA + [3-hydroxybutanoate]n
[3-hydroxybutanoate](n+1) + CoA
-
-
-
-
?
(R)-3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate](n+1) + CoA
D2Z0B8 and D2Z0B6
-
-
-
?
(R)-3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate](n+1) + CoA
D2Z0B8 and D2Z0B6
-
-
-
?
(R)-3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate](n+1) + CoA
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PHB synthase exhibits positive cooperativity
-
-
?
(R)-3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate](n+1) + CoA
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PHB synthase exhibits positive cooperativity
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-
?
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
-
-
-
-
?
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
-
-
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
-
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a low-molecular-weight, Mn = 20000
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-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
-
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a low-molecular-weight, Mn = 20000
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-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
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-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a relatively high molecular weight, Mn = 890000
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-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
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-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a relatively high molecular weight, Mn = 890000
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-
?
additional information
?
-
the PhaC from BAcillus cereus also shows a polyhydroxybutanoate hydrolyzing activity, time-dependent change in inverse of degree of polymerization during intracellular P(3HB) degradation at a culture temperature of 37°C, overview
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-
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additional information
?
-
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enzyme shows alcoholytic cleavage of PHA chains induced by endogenous ethanol
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-
-
additional information
?
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D2Z0B8 and D2Z0B6
enzyme shows alcoholytic cleavage of PHA chains induced by endogenous ethanol
-
-
-
additional information
?
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enzyme shows both PHA polymerization and alcoholysis activities. For alcoholysis, PhaRC utilizes various alcohols other than ethanol for alcoholysis, leading to the PHA carboxy terminus modified with thiol, alkynyl, hydroxy, and benzyl groups
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additional information
?
-
the PhaC from BAcillus cereus also shows a polyhydroxybutanoate hydrolyzing activity, time-dependent change in inverse of degree of polymerization during intracellular P(3HB) degradation at a culture temperature of 37°C, overview
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-
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additional information
?
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D2Z0B8 and D2Z0B6
enzyme shows alcoholytic cleavage of PHA chains induced by endogenous ethanol
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-
-
additional information
?
-
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enzyme shows both PHA polymerization and alcoholysis activities. For alcoholysis, PhaRC utilizes various alcohols other than ethanol for alcoholysis, leading to the PHA carboxy terminus modified with thiol, alkynyl, hydroxy, and benzyl groups
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additional information
?
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the 3-hydroxyvalerate molar fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is significantly affected by the type of the precursor used and their respective feeding time
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additional information
?
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the 3-hydroxyvalerate molar fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is significantly affected by the type of the precursor used and their respective feeding time
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additional information
?
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3-hydroxyvaleryl-CoA, 4-hydroxybutyryl-CoA, and 3-hydroxydecanoyl-CoA are not accepted as substrates
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additional information
?
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3-hydroxyvaleryl-CoA, 4-hydroxybutyryl-CoA, and 3-hydroxydecanoyl-CoA are not accepted as substrates
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
-
-
-
-
?
3-hydroxybutyryl-CoA + 3-hydroxyvalerate
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) + CoA
-
-
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
D2Z0B8
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a low-molecular-weight, Mn = 20000
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
D2Z0B8
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a low-molecular-weight, Mn = 20000
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
D2Z0B9
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a relatively high molecular weight, Mn = 890000
-
-
?
3-hydroxybutyryl-CoA + [(R)-3-hydroxybutanoate]n
[(R)-3-hydroxybutanoate]n+1 + CoA
D2Z0B9
PhaRCBm synthesizes (R)-3-hydroxybutanoate, P(3HB), with a relatively high molecular weight, Mn = 890000
-
-
?
additional information
?
-
D2Z0B8
the PhaC from BAcillus cereus also shows a polyhydroxybutanoate hydrolyzing activity, time-dependent change in inverse of degree of polymerization during intracellular P(3HB) degradation at a culture temperature of 37°C, overview
-
-
-
additional information
?
-
D2Z0B8
the PhaC from BAcillus cereus also shows a polyhydroxybutanoate hydrolyzing activity, time-dependent change in inverse of degree of polymerization during intracellular P(3HB) degradation at a culture temperature of 37°C, overview
-
-
-
additional information
?
-
-
the 3-hydroxyvalerate molar fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is significantly affected by the type of the precursor used and their respective feeding time
-
-
-
additional information
?
-
-
the 3-hydroxyvalerate molar fraction in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) is significantly affected by the type of the precursor used and their respective feeding time
-
-
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Mg2+
-
addition of Mg2+ shows the strongest activation effect. However, high enzyme activity without Mg2+ ions is observed, when other ions are present, suggesting that Mg2+ ions do not serve as cofactors
additional information
-
in the absence of salts the granule-bound PHB synthase still exhibits about 40% of the maximum activity. Enzyme activity is strongly enhanced by slightly increasing the ionic strength independent of the salt
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
acetyl phosphate
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activates the enzyme and the level of activation is dependent on the concentration of acetyl phosphate supplementation
additional information
-
upion growth in in N2 deficient medium, cell biomass remains almost steady from 0 h after transfer to production medium till the end of fermentation (120 h), while polyhydroxybutanoate yield shows an increase from 0.533 g/l at 0 h to 4g/l by 48 h and later gradually decreases, with increase in polyhydroxybutanoate accumulation increase from 11% to 77% by 96 h
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
IC50 VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
6.5 - 8.5
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pH 6.5: about 30% of maximal activity, pH 8.5: about 85% of maximal activity
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
20 - 70
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20°C: about 50% of maximal activity, 70°C: about 50% of maximal activity
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
-
highest P(3HB) production of 2.38 g/l at 68 wt% attained with crude palm kernel oil as the sole carbon source
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highest P(3HB) production of 2.38 g/l at 68 wt% attained with crude palm kernel oil as the sole carbon source
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
-
PHB synthase can not be released from the PHB granules, indicating a covalent attachment to the PHB core
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PHB synthase can not be released from the PHB granules, indicating a covalent attachment to the PHB core
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
a synthetic operon for polyhydroxyalkanoate biosynthesis designed to yield high levels of PHA synthase activity in vivo is constructed by positioning a genetic fragment encoding beta-ketothiolase and acetoacetyl-CoA reductase behind a modified synthase gene containing an Escherichia coli promoter and ribosome binding site. Plasmids containing the synthetic operon and the native Alcaligenes eutrophus PHA operon are transformed into Escherichia DH5 alpha and analyzed for polyhydroxybutyrate production. The molecular weight of polymer isolated from recombinant Escherichia coli containing the modified synthase construct is lower than that of the polymer from Escherichia coli containing the native Alcaligenes eutrophus operon. A further decrease in polyester molecular weight is observed with increased induction of the PHA biosynthetic genes in the synthetic operon. Comparison of the enzyme activity levels of PHA biosynthetic enzymes in a strain encoding the native operon with a strain possessing the synthetic operon indicates that the amount of polyhydroxyalkanoate synthase in a host organism plays a key role in controlling the molecular weight and the polydispersity of polymer
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expression of PhaRCBm, and as hybrid enzyme PhaRYB4CBm with Bacillus cereus YB-4, PhaRCYB4 in Escherichia coli JM109
expression of PhaRCYB4, and as hybrid enzyme PhaRYB4CBm with Bacillus megaterium NBRC15308, PhaRCBm in Escherichia coli JM109
gene phaCUSMAA2-4, DNA and amino acid sequence determination and analysis, expression in and complementation of mutant Cupriavidus necator PHB-4 deficient in PHA synthesis, expression in Escherichia coli strain S17-1
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gene phbCPs encoded in the phb operon, DNA and amino acid sequence determination and analysis, sequence comparisons and phylogenetic tree, the genetic organization of phb operon shows a putative promoter region, followed by phbBPs-phbAPs-phbCPs, with phbRPs encoding a putative transcriptional activator that is located in the opposite orientation, upstream of phbBACPs. Heterologous expression of phbCPs from pGEM3ABex vector in Escherichia coli JM109 resulting in P(3HB) accumulation of up to 40% of dry cell weight
the phaC coding region is subcloned into vector pBBR1-JO2 under lac promoter control. The resulting plasmid, pQQ4, mediates PHB accumulation in the mutant Ralstonia eutropha PHBN4 and recombinant Escherichia coli JM109(pBHR69)
ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
additional information
additional information
construction of enzyme hybrids of PhaC from Bacillus megaterium and Bacillus cereus, i.e. PhaRBmCYB4 and PhaRYB4CBm. The molecular weight of P(3HB) synthesized by PhaRCYB4 decreased with increasing culture time and temperature, time-dependent behavior is observed for hybrid synthase PhaRBmCYB4, but not for PhaRYB4CBm, thus the molecular weight change is caused by the PhaCYB4 subunit
additional information
-
construction of enzyme hybrids of PhaC from Bacillus megaterium and Bacillus cereus, i.e. PhaRBmCYB4 and PhaRYB4CBm. The molecular weight of P(3HB) synthesized by PhaRCYB4 decreased with increasing culture time and temperature, time-dependent behavior is observed for hybrid synthase PhaRBmCYB4, but not for PhaRYB4CBm, thus the molecular weight change is caused by the PhaCYB4 subunit
-
additional information
construction of enzyme hybrids of PhaC from Bacillus megaterium and Bacillus cereus, i.e. PhaRBmCYB4 and PhaRYB4CBm. The molecular weight of P(3HB) synthesized by PhaRCYB4 decreased with increasing culture time and temperature, time-dependent behavior is observed for hybrid synthase PhaRBmCYB4, but not for PhaRYB4CBm, thus the molecular weight change is caused by the PhaCYB4 subunit
additional information
-
construction of enzyme hybrids of PhaC from Bacillus megaterium and Bacillus cereus, i.e. PhaRBmCYB4 and PhaRYB4CBm. The molecular weight of P(3HB) synthesized by PhaRCYB4 decreased with increasing culture time and temperature, time-dependent behavior is observed for hybrid synthase PhaRBmCYB4, but not for PhaRYB4CBm, thus the molecular weight change is caused by the PhaCYB4 subunit
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
synthesis
synthesis
-
enzyme shows both polyhydroxyalkanoate polymerization and alcoholysis activities, unsing various alcohols other than ethanol for alcoholysis.. Through the use of bifunctional compounds for alcoholysis, the polyhydroxyalkanoate carboxy terminus can be modified with thiol, alkynyl, hydroxy, and benzyl groups, resulting in the functionalization of the polyhydroxyalkanoate carboxy terminus
synthesis
-
enzyme shows both polyhydroxyalkanoate polymerization and alcoholysis activities, unsing various alcohols other than ethanol for alcoholysis.. Through the use of bifunctional compounds for alcoholysis, the polyhydroxyalkanoate carboxy terminus can be modified with thiol, alkynyl, hydroxy, and benzyl groups, resulting in the functionalization of the polyhydroxyalkanoate carboxy terminus
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LINKS TO OTHER DATABASES (specific for EC-Number 2.3.1.B5)
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