Probe Development Summary of Inhibitors of 12-hLO (12-human lipoxygenase)
Lipoxygenases are a class of non-heme iron-containing enzymes. There are three major human lipoxygenses: 5-, 12, and 15-hLO, whose primary enzymatic difference lies in their site-specific oxidation of arachidonic acid. The products of lipoxygenases are precursors of hormones such as leukotrienes and lipoxins, which have been implicated as critical in a variety of inflammatory diseases and more ..
Depositor Specified Assays
Source: NIH Chemical Genomics Center [NCGC]
Assay Submitter: Holman, T.R., University of California, Santa Cruz
Screening Center PI: Christopher P. Austin, NIH
Probe Development: NIH Chemical Genomics Center [NCGC]
NIH Grant Number: MH081283-01
Lipoxygenases are a class of non-heme iron-containing enzymes. There are three major human lipoxygenses: 5-, 12, and 15-hLO, whose primary enzymatic difference lies in their site-specific oxidation of arachidonic acid. The products of lipoxygenases are precursors of hormones such as leukotrienes and lipoxins, which have been implicated as critical in a variety of inflammatory diseases and cancers. 15-hLO-1 has higher expression in human prostate tumors, compared with adjacent tissue, and this expression correlates with the virulency of the cancer. Also, the 15-hLO-1 metabolite of linoleic acid, 13-(S)-hydroxyoctadecadienoic acid, is detected in adenocarcinoma tissue, indicating a pro-tumorigenic role in prostate tumor development for 15-hLO-1.
Inhibitors of lipoxygenase are found in three broad categories reflecting the mode of action: reductive, catalytic and allosteric. The reductive inhibitors convert the active, ferric enzyme to the inactive, ferrous form. The catalytic inhibitors act as competitive inhibitors. The allosteric inhibitors, are however different in their kinetic properties and do not bind to the catalytic site, but an allosteric site, whose exact position is not known. The presence of such a site allows for targeting two sites in lipoxygenase, the allosteric and the catalytic sites, which may have different SARs and different pharmacophore profiles.
The overall goal of Molecular Libraries Initiative Grant MH081283-01 is to screen against three lipoxygenase isozymes; reticulocyte 15-hLO-1, epidermal 15-hLO-2 and platelet 12-hLO, with the aim of finding selective inhibitors specific for each isozyme. The design of selective inhibitors of lipoxygenases has been particularly challenging in the field.
This particular summary assay focuses on small molecule probe development of 12-hLO. A chemical probe for this project is defined as follows: a small molecule compound which inhibits 12-hLO enzyme with an IC50 of 1 uM or less in the secondary cuvette assay. A desired but not required characteristic is selectivity. A probe should preferably inhibit the 12hLO enzyme at an IC50 10 times lower than it would 15-hLO-1 and 15-hLO-2.
Recommendations for the scientific use of probe described in this assay:
Small molecule probes from this project will exhibit potent inhibition of 12-hLO, yet will not inhibit the closely related 15-hLO-1 and 15-hLO-2. The probe should be useful for in vitro studies of 12-hLO but may also be utilized as a starting point for the development of 12-hLO effectors in cellular or animal models.
Please see related BioAssay(s) for all protocols relevant to this probe development project: AID 1452
AID 1452: This assay is main primary screen for inhibitors of 12-hLO (12-human lipoxygenase). A collection of 151,834 compounds were screened in a concentration response dependent manner.
This summary assay will be updated as additional screens are run and small molecule probes have been developed.