5lc8
Crystal Structure of specific mutant from Pseudomonas aeruginosa Lipoxygenase at 1.8A resolution
Structural highlights
FunctionLOX_PSEAI In presence of oxygen, converts oleic acid into (S)-(E)-10-hydroperoxy-8-octadecenoic acid (HPOD), which spontaneously decomposes to the corresponding (E)-10-hydroxy-8-octadecenoic acid (HOD). In vivo, the reaction leads to the dihydroxy derivative (E)-7,10-dihydroxy-8-octadecenoic acid (DHOD), so that the three hydroxy-fatty acids can be isolated from the culture medium. Also active on linoleic acid and linolenic acid. Almost not active on arachidonic acid. Publication Abstract from PubMedSecreted LOX from Pseudomonas aeruginosa (PA-LOX) has previously been identified as arachidonic acid 15S-lipoxygenating enzyme. Here we report that the substitution of Ala420Gly in PA-LOX leads to an enzyme variant with pronounced dual specificity favoring arachidonic acid 11R-oxygenation. When compared with other LOX-isoforms the oxygen affinity of wild-type PA-LOX is 1-2 orders of magnitude lower (oxygen Km of 0.4mM) but Ala420Gly exchange improved the oxygen affinity (oxygen Km of 0.2mM). Experiments with stereo-specifically deuterated linoleic acid indicated that the formation of both 13S- and 9R-HpODE involves abstraction of the proS-hydrogen from C11 of the fatty acid backbone. To explore the structural basis for the observed functional changes (altered specificity, improved oxygen affinity) we solved the crystal structure of the Ala420Gly mutant of PA-LOX at 1.8A resolution and compared it with the wild-type enzyme. Modeling of fatty acid alignment at the catalytic center suggested that in the wild-type enzyme dioxygen is directed to C15 of arachidonic acid by a protein tunnel, which interconnects the catalytic center with the protein surface. Ala420Gly exchange redirects intra-enzyme oxygen diffusion by bifurcating this tunnel so that C11 of arachidonic acid also becomes accessible for oxygen insertion. The crystal structure of Pseudomonas aeruginosa lipoxygenase Ala420Gly mutant explains the improved oxygen affinity and the altered reaction specificity.,Kalms J, Banthiya S, Yoga EG, Hamberg M, Holzhutter HG, Kuhn H, Scheerer P Biochim Biophys Acta. 2017 Jan 13. pii: S1388-1981(17)30003-3. doi:, 10.1016/j.bbalip.2017.01.003. PMID:28093240[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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