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  • Title: An NAD-linked acetoacetyl-CoA reductase from Zoogloea ramigera I-16-M.
    Author: Shuto H, Fukui T, Saito T, Shirakura Y, Tomita K.
    Journal: Eur J Biochem; 1981 Aug; 118(1):53-9. PubMed ID: 7026239.
    Abstract:
    An NAD-linked acetoacetyl-CoA reductase of Zoolgoea ramigera I-16-M was purified to electrophoretic homogeneity. In contrast to the D(-)-3-hydroxybutyryl-CoA-specific NADP-linked acetoacetyl-CoA reductase from the same bacterium [Saito, T. et al (1977) Arch. Microbiol. 114, 211 - 217], the purified enzyme was strictly stereospecific to L(+)-3-hydroxybutyryl-CoA, and was active not only with NAD+ but also with NADP+, although NADP+ was less effective than NAD+ as coenzyme. The enzyme showed a pH optimum at 6.3 for the reduction of acetoacetyl-CoA and at 8.0 for the oxidation of L(+)-3-hydroxybutyryl-CoA. In the reduction reaction, Km values for acetoacetyl-Coa and NADH were 8.8 microM and 6.5 microM, respectively, and in the oxidation reaction, Km values for L(+)-3-hydroxybutyryl-CoA and DNA+ were 7.0 microM and 32 microM, respectively. Among various 3-hydroxyacyl-CoAs tested, L(+)-3-hydroxybutyryl-CoA and L(+)-3-hydroxyvaleryl-CoA were the most active substrates. Poly(3-hydroxybutyrate) synthesis from acetyl-CoA, by a system reconstituted from purified preparations of 3-oxothiolase, acetoacetyl-CoA reductase and poly(3-hydroxybutyrate) synthase, was observed when the NADP-linked but not the NAD-linked reductase was used. These findings indicate that the NAD-linked acetoacetyl-CoA reductase is not directly involved in the biosynthesis of poly(3-hydroxybutyrate).
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