- Partial purification and characterization of β-ketothiolase from Alcaligenes sp. SH-69
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Oh, Deok Hwan , Chung, Chung Wook , Kim, Jeong Yoon , Rhee, Young Ha
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J. Microbiol. 1997;35(4):360-364.
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 Abstract
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A β-ketothiolase was purified 180-fold from the cell extracts of Alcaligenes sp. SH-69 by a series of chromatography on DEAE-Dephadex A-50, Sephacryl S-200, and hydrozyapatitie columns, The optimum pH values of the partially purified enzyme were 7.5 for condensation reaction and 8.3 for thiolysis reaction. The K_m valued for acetoacetyl-CoA and free CoASH in the thiolusis in the condensation reaction was 0.70mM. The condensation reaction of the β-ketothiolase was inhibited even by low concentrations of free CoASH(K_I= 30.4 uM). Pretreatment of the enzyme with NADH and NADPH markedly inhibited the thiolysis reaction of the enzyme. The potent inhibition of the enzyme by sulfhydryl reagents suggests the involvement of cystein residue in the active site.
- Biosynthesis of Poly-β-Hydrozyalkanoates by Bacillus thuringiensis R-510
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Lee, Kang Tae , Kim, Jeong Yoon , Rhee, young Ha , Bae, Kyung Sook , Kim, Young Baek
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J. Microbiol. 1995;33(1):59-65.
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Abstract
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Synthesis and accumulation of Poly-β-Hydrozyalkanoates (PHA) in Bacillus thuringiensis R-510 isolated from soil were investigatd. This organism was resistant to relatively higj concentration of propionate and had a capability of accumulatinf copolymers consisting of 3-hydroxybutyrate(3HB) and 3-hydroxyvalerate(3HV) when the medium was supplemented with propionate as a precursor, The PHA content maximally reached up to 44.5% of dry cell weight in the presence of 0.1% propionate. The molar fraction of 3HV in the copolymer was increased from 19.4 to 80,2 mol% by adding 0.05 to 0.5% propionate to glucose medium. The addition of propionate during exponential or stationary phase of cell growth was less effective for the enhancement of 3HV content in the copolymer, although cell mass and PHA content were not affected by the time of propionate addition. PHB homopolymer and copolymer produced by B. thuringiensis R-510 were measured to have number average molecular weights in the range of 53,000 to 65,000. Polydispersity indices were between 1.5 and 2.2. Some of the produced polymers had bimodal molecular weight distribution.
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