Enzymatic synthesis of fatty alcohols in Brassica oleracea

Acetone powder extracts prepared from young broccoli (Brassica oleracea) leaves catalyzed palmitaldehyde reduction to the corresponding alcohol with TPNH as the preferred reducing agent. The aldehyde reductase was purified 13-fold by ammonium sulphate fractionation and Sephadex G-100 gel filtration. The pH optimum was about 5.6 and apparent K_m was 5 × 10⁻⁵m and 7 × 10⁻⁵m with respect to TPNH and palmitaldehyde, respectively. The enzyme was severely inhibited by iodoacetic acid, iodoacetamide, N-ethyl maleimide and parachloromercuric benzoate, suggesting the presence of SH groups essential for activity. Another protein fraction obtained from the same acetone powder extract by Sephadex G-100 gel filtration showed palmityl and stearyl-CoA reductase activity which required DPNH, and the product of this reaction was the corresponding aldehyde. It is, therefore, concluded that acyl-CoA reductase converts fatty-CoA into aldehyde which in turn is reduced by aldehyde reductase to the alcohol in B. oleracea.