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LIPOXYGENASE-1 (SOYBEAN) AT 100K, Q495A MUTANT
Structural highlights
FunctionLOX1_SOYBN Plant lipoxygenase may be involved in a number of diverse aspects of plant physiology including growth and development, pest resistance, and senescence or responses to wounding. With linoleate as substrate, L-1 shows a preference for carbon 13 as the site for hydroperoxidation (in contrast to L-2 and L-3, which utilize either carbon 9 or 13). At pH above 8.5, only (9Z,11E,13S)-13-hydroperoxyoctadeca-9,11-dienoate is produced, but as the pH decreases, the proportion of (9S)-hydroperoxide increases linearly until at pH 6.0 it represents about 25 % of the products.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedLipoxygenases are an important class of non-heme iron enzymes that catalyze the hydroperoxidation of unsaturated fatty acids. The details of the enzymatic mechanism of lipoxygenases are still not well understood. This study utilizes a combination of kinetic and structural probes to relate the lipoxygenase mechanism of action with structural modifications of the iron's second coordination sphere. The second coordination sphere consists of Gln(495) and Gln(697), which form a hydrogen bond network between the substrate cavity and the first coordination sphere (Asn(694)). In this investigation, we compared the kinetic and structural properties of four mutants (Q495E, Q495A, Q697N, and Q697E) with those of wild-type soybean lipoxygenase-1 and determined that changes in the second coordination sphere affected the enzymatic activity by hydrogen bond rearrangement and substrate positioning through interaction with Gln(495). The nature of the C-H bond cleavage event remained unchanged, which demonstrates that the mutations have not affected the mechanism of hydrogen atom tunneling. The unusual and dramatic inverse solvent isotope effect (SIE) observed for the Q697E mutant indicated that an Fe(III)-OH(-) is the active site base. A new transition state model for hydrogen atom abstraction is proposed. Structural and functional characterization of second-coordination sphere mutants of soybean lipoxygenase-1.,Tomchick DR, Phan P, Cymborowski M, Minor W, Holman TR Biochemistry. 2001 Jun 26;40(25):7509-17. PMID:11412104[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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