Escherichia coli beta-hydroxydecanoyl thioester dehydrase reacts with native C10 acyl-acyl-carrier proteins of plant and bacterial origin.
beta-Hydroxydecanoyl-[acyl-carrier-protein] dehydrase catalyzes the essential step in the formation of unsaturated fatty acids in Escherichia coli. This reaction was characterized with native C10 acyl-acyl-carrier protein (ACP) structures in both an aqueous phase system and a substrate immobilization assay system. The dehydrase is equally active with E. coli ACP, recombinant ACP-I derived from spinach, or protein A:ACP-I fusion (acyl-thioesters). There were differences among the substrates in terms of the equilibrium product distribution. Both E. coli acyl-ACP and recombinant acyl-ACP-I as cosubstrates with beta-OH 10:0, trans-2 10:1, or cis-3 10:1 yielded about equal amounts (37 mol%) of the two monoenes regardless of the initial substrate. In contrast, the fusion acyl-ACP-I yielded only 17 mol% cis-3 10:1 with 49 mol% trans-2 10:1 present at equilibrium. These equilibrium values for native cis-3 10:1 are higher than those reported previously for the dehydrase using N-acetylcysteamine thioesters as substrates. The Km values for each beta-OH 10:0 ACP substrate were similar to each other and within the range of in vivo concentrations (5-10 microM). Dehydrase reactivity depends more on acyl chain length than ACP structure or origin and is therefore different from other branch point ACP-utilizing enzymes (plant and bacterial) which discriminate according to ACP structure (D. J. Guerra, J. B. Ohlrogge, and M. Frentzen, 1986, Plant Physiol. 82, 448-453).
Guerra
D J
DJ
Institute of Biological Chemistry, Washington State University, Pullman 99164-6340.
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JA
D000213:Acyl Carrier Protein / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D004926:Escherichia coli / Q000201:enzymology*; D006836:Hydro-Lyases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D014675:Vegetables
D000213:Acyl Carrier Protein; D011994:Recombinant Proteins; D006836:Hydro-Lyases