Biosynthesis of Lipids

Abstract

During the late 1930s, Barker isolated an anaerobic bacterium which he called Clostridium kluyveri. This organism is able to grow on a mixture of acetate and ethanol and produces n-butyrate and n-caproate. From this organism, Barker and Stadtman obtained cell-free extracts which could carry the reactions leading to the C4 and C6 acids. Ethanol is oxidized to acetic acid in two steps, respectively, catalyzed by alcohol dehydrogenase and an acetaldehyde dehydrogenase depending on the presence of coenzyme A:

$$ \begin{array}{c}\mathrm{Malonyl}\ \mathrm{CoA}+\mathrm{ACP}\hbox{-} \mathrm{S}\mathrm{H} = \mathrm{Malonyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{C}\mathrm{oASH}\\ {}\mathrm{Acetyl}\ \mathrm{CoA}+\mathrm{ACP}\hbox{-} \mathrm{S}\mathrm{H}\kern0.37em =\mathrm{Acetyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{C}\mathrm{oASH}\\ {}\mathrm{Acetyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}\kern0.45em +\kern0.45em \mathrm{Malonyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP} = \mathrm{Acetoacetyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{ACP}\hbox{-} \mathrm{S}\mathrm{H}+\mathrm{C}{\mathrm{O}}_2\\ {}\mathrm{Acetoacetyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{NAD}\mathrm{PH}+{\mathrm{H}}^{+} = \upbeta \hbox{-} \mathrm{hydroxybutyryl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{NAD}{\mathrm{P}}^{+}\\ {}\upbeta \hbox{-} \mathrm{hydroxybutyryl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP} = \mathrm{Crotonyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+{\mathrm{H}}_2\mathrm{O}\\ {}\mathrm{Crotonyl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{NAD}\mathrm{PH}+{\mathrm{H}}^{+} = \mathrm{Butyryl}\hbox{-} \mathrm{S}\hbox{-} \mathrm{ACP}+\mathrm{NAD}{\mathrm{P}}^{+}\end{array} $$