Temperature-induced differential kinetic properties between an initial burst and the following steady state in membrane-bound enzymes: Studies on lathosterol 5-desaturase

Hideaki Nishino, Jun Nakaya, Shinya Nishi, Takao Kurosawa, Teruo Ishibashi

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

The NADH-dependent lathosterol 5-desaturation reaction that forms 7- dehydrocholesterol is biphasic, an initial burst followed by steady state. The steady-state phase is slower than the burst phase, because the latter diffusion of the lathosterol substrate within the microsomal membrane must occur before the next reaction can take place [Y. Takakuwa, H. Nishino, Y. Ishibe, and T. Ishibashi (1994) J. Biol. Chem. 269, 27889-27893]. In the present study, changes in the structure and function of the membrane were examined by measurement of the Arrhenius activation energy of lathosterol 5- desaturase at various temperatures between 2 and 45°C. At the burst phase, there was a lack of discontinuity in the Arrhenius plots at the presumed phase transition temperature for the microsomal membrane. However, the plots of the activities of the steady state showed breaks at around 17 and 32°C. It was concluded that phospholipid phase transition affects the steady-state phase but not the burst phase. Furthermore, treatment of microsomes with low concentrations of deoxycholate, known to perturb the membrane integrity, resulted in a break of the activation energy of the burst phase. These results have revealed further evidence for our previous model suggesting interaction between the substrate and enzyme within the microsomal membrane via lateral diffusion.

Original languageEnglish
Pages (from-to)298-304
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume339
Issue number2
DOIs
Publication statusPublished - 1997 Mar 15
Externally publishedYes

Keywords

  • Arebenius plots
  • lateral diffusion
  • lathosterol 5-desaturation
  • microsomal membrane
  • phase transition

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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