title: Purification and properties of acyl coenzyme A thioesterase II from Rhodopseudomonas sphaeroides.
abstract: A high molecular weight acyl coenzyme A (acyl-CoA) thioesterase, designated thioesterase II, has been purified 5300-fold from photoheterotrophically grown cells of Rhodopseudomonas sphaeroides. In contrast to R. sphaeroides acyl-CoA thioesterase I [Boyce, S.G., & Lueking, D.R. (1984) Biochemistry 23, 141-147], thioesterase II has a native molecular mass (Mr) of 120,000, is capable of hydrolyzing saturated and unsaturated acyl-CoA substrates with acyl chain lengths ranging from C4 to C18, and is completely insensitive to the serine esterase inhibitor diisopropyl fluorophosphate. Palmitoyl-CoA and stearoyl-CoA are the preferred (lowest Km) saturated acyl-CoA substrates and vaccenoyl-CoA is the preferred unsaturated substrate. However, comparable Vmax values were obtained with a variety of acyl-CoA substrates. Unlike a similar thioesterase present in cells of Escherichia coli [Bonner, W.M., & Bloch, K. (1972) J. Biol. Chem. 247, 3123-3133], R. sphaeroides thioesterase II displays a high ratio of decanoyl-CoA to palmitoyl-CoA activities and exhibits little ability to hydrolyze 3-hydroxyacyl-CoA substrates. Only 3-hydroxydodecanoyl-CoA supported a measurable rate of enzyme activity. With the purification of thioesterase II, the enzymes responsible for greater than 90% of the acyl-CoA thioesterase activity present in cell-free extracts of R. sphaeroides have now been identified.
authors.forename: T
authors.initials: T
authors.lastname: Seay
authors.forename: D R
authors.initials: DR
authors.lastname: Lueking
mesh_terms: D004591:Electrophoresis, Polyacrylamide Gel; D064429:Fatty Acid Synthases / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D010170:Palmitoyl-CoA Hydrolase / Q000302:isolation & purification* / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D064429:Fatty Acid Synthases; D013869:Thiolester Hydrolases; C022738:thioesterase II; D010170:Palmitoyl-CoA Hydrolase