These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Inhibition kinetics and affinity labeling of bacterial squalene:hopene cyclase by thia-substituted analogues of 2, 3-oxidosqualene.
    Author: Zheng YF, Abe I, Prestwich GD.
    Journal: Biochemistry; 1998 Apr 28; 37(17):5981-7. PubMed ID: 9558334.
    Abstract:
    Five sulfur-containing analogues of 2,3-oxidosqualene (OS) were evaluated as inhibitors of squalene:hopene cyclase (SHC) from Alicyclobacillus acidocaldarius. In these analogues, sulfur replaces carbons at C-6, C-10, C-14, C-18, or C-19 of OS. Each analogue was a submicromolar inhibitor of SHC with IC50 values ranging from 60 to 570 nM. Enzyme inhibition kinetic analysis was performed using homogeneous recombinant A. acidocaldarius SHC. While analogues 9 (S-14, Ki = 109 nM, kinact = 0.058 min-1) and 11 (S-19, Ki = 83 nM, kinact = 0.054 min-1) were time-dependent inhibitors of SHC, analogues 7 (S-6, Ki = 127 nM) and 8 (S-10, Ki = 971 nM) showed no time dependency with SHC. Analogue 10 (S-18) was the most potent inhibitor and showed time-dependent irreversible inhibition (Ki = 31 nM, kinact = 0.071 min-1). Kinetic analysis for the five analogues with purified rat liver OSLC was conducted to compare the vertebrate and prokaryotic enzymes. Affinity labeling experiments, using either [17-3H]10 or [22-3H]10 with crude and with pure recombinant SHC, clearly showed specific labeling. A single major radioactive band at 72 kDa on SDS-PAGE indicated that irreversible covalent modification of SHC had occurred. These results suggest that the presence of sulfur at C-18 of OS can interrupt the cyclization and that an intermediate partially cyclized cation may be captured by a nucleophilic residue of the SHC active site.
    [Abstract] [Full Text] [Related] [New Search]