Biochemical Characteristics of a Palmitoyl Acyl Carrier Protein Thioesterase Purified from Iris pseudoacorus

  • Kang, Han-Chul (Division of Biochemistry, National Agricultural Science and Technology Institute, Rural Development Administration) ;
  • Hwang, Young-Soo (Division of Biochemistry, National Agricultural Science and Technology Institute, Rural Development Administration)
  • Received : 1996.05.15
  • Published : 1996.09.30


The palmitoyl acyl carrier protein (ACP) specific thioesterase (EC from Iris pseudoacorus was purified and characterized. The thioesterase which was very unstable in relatively high salt concentrations was eluted using a co-gradient of Triton X-100 and low concentration of KCl or Na-phosphate from Q-Sepharose, DEAE-Sepharose, and hydroxyapatite chromatography. SDS-PAGE analysis showed a single band with a molecular weight of 35,000. The native molecular weight of approximately 37,000 was estimated by Sephacryl S-200 chromatography, indicating that the enzyme is a monomer. The thioesterase activity was inhibited about 75% and 50% by N-ethylmaleimide (2 mM) and phenylmethylsulfonyl fluoride (2 mM). respectively. The N-ethylmaleimide-inactivation was protected by sodium palmitate but the inactivation with phenylmethylsulfonyl fluoride was not protected. Oxidation of thiols by 2 mM 5.5'-dithio-bis-(2-nitrobenzoic acid) resulted in 65% inactivation of the enzyme. These results suggest that a cysteinyl residue is essential to the catalytic reaction of the enzyme. The enzyme activity was increased by sodium citrate and also by $Cu^{2+}$


active site;co-gradient protein elution;palmitoyl acyl carrier protein thioesterase


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