Purification and properties of an esterase from Cucurbita maxima fruit tissue

Amanda Nourse, Johan C. Schabort, Heini W. Dirr, Ian A. Dubery

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


An esterase from the fruit of Cucurbita maxima was purified to apparent homogeneity. The enzyme displays an Mr, of 36 000, a pI value of 4.9, a Stokes radius of 2.70 nm, diffusion coefficient of 9.25 × 10 $ ̄7 cm2/sec, possesses a homogeneous dimeric quaternary structure with a subunit Mr, of 18 000. High esterolytic activity was observed with indophenyl acetate (1510μmol/min/mg protein and p-nitrophenyl acetate (648μmol/min/mg protein) while the enzyme displayed no carboxypeptidase, amidase, proteinase or aminopeptidase activities. Based on indophenyl acetate as substrate, the esterase has an optimum pH of 7.5 to 8.9 and a Km value of 0. 14 mM at pH 8.0. The esterolytic activity is strongly inhibited by mercaptide-forming and alkylating thiol reagents and by diisopropyl fluorophosphate and phenylmethylsulphonyl fluoride. Product inhibition by indophenyl was competitive (apparent Ki = 90,μM) relative to indophenol acetate and parabolic. Acetate was without effect.

Original languageEnglish
Pages (from-to)379-383
Number of pages5
Issue number2
Publication statusPublished - 1989


  • Cucurbita maxima
  • Cucurbitaceae
  • esterase.

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Plant Science
  • Horticulture


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