Title
Identification of the Substrate Access Portal of 5-Lipoxygenase
Document Type
Article
Publication Date
10-20-2015
Abstract
The overproduction of inflammatory lipid mediators derived from arachidonic acid contributes to asthma and cardiovascular diseases, among other pathologies. Consequently, the enzyme that initiates the synthesis of pro-inflammatory leukotrienes, 5-lipoxygenase (5-LOX), is a target for drug design. The crystal structure of 5-LOX revealed a fully encapsulated active site; thus the point of substrate entry is not known. We asked whether a structural motif, a "cork" present in 5-LOX but absent in other mammalian lipoxygenases, might be ejected to allow substrate access. Our results indicate that reduction of cork volume facilitates access to the active site. However, if cork entry into the site is obstructed, enzyme activity is significantly compromised. The results support a model in which the "cork" that shields the active site in the absence of substrate serves as the active site portal, but the "corking" amino acid Phe-177 plays a critical role in providing a fully functional active site. Thus, the more appropriate metaphor for this structural motif is a "twist-and-pour" cap. Additional mutagenesis data are consistent with a role for His-600, deep in the elongated cavity, in positioning the substrate for catalysis.
Publication Source (Journal or Book title)
Biochemistry
First Page
6333
Last Page
42
Recommended Citation
Mitra, S., Bartlett, S. G., & Newcomer, M. E. (2015). Identification of the Substrate Access Portal of 5-Lipoxygenase. Biochemistry, 54 (41), 6333-42. https://doi.org/10.1021/acs.biochem.5b00930