1FGR

LIPOXYGENASE-1 (SOYBEAN) AT 100K, Q697E MUTANT

Summary for 1FGR

• Entry DOI: 10.2210/pdb1fgr/pdb
• Related: 1F8N 1FGM 1FGO 1FGQ 1FGT 1YGE
• Descriptor: SEED LIPOXYGENASE-1, FE (III) ION (3 entities in total)
• Functional Keywords: dioxygenase, lipoxygenase, metalloprotein, fatty acids, oxidoreductase
• Biological source: Glycine max (soybean)
• Cellular location: Cytoplasm: P08170
• Total number of polymer chains: 1
• Total formula weight: 94536.96

Authors

Tomchick, D.R.,Minor, W.,Holman, T. (deposition date: 2000-07-28, release date: 2001-07-04, Last modification date: 2023-08-09)

Primary citation

Tomchick, D.R.,Phan, P.,Cymborowski, M.,Minor, W.,Holman, T.R.
Structural and functional characterization of second-coordination sphere mutants of soybean lipoxygenase-1.
Biochemistry, 40:7509-7517, 2001

PubMed Abstract: Lipoxygenases 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.

PubMed: 11412104
DOI: 10.1021/bi002893d

Experimental method

X-RAY DIFFRACTION (1.6 Å)