Molecular basis for the catalytic inactivity of a naturally occurring near-null variant of human ALOX15.

Abstract

Mammalian lipoxygenases belong to a family of lipid-peroxidizing enzymes, which have been implicated in cardiovascular, hyperproliferative and neurodegenerative diseases. Here we report that a naturally occurring mutation in the hALOX15 gene leads to expression of a catalytically near-null enzyme variant (hGly422Glu). The inactivity may be related to severe misfolding of the enzyme protein, which was concluded from CD-spectra as well as from thermal and chemical stability assays. In silico mutagenesis experiments suggest that most mutations at hGly422 have the potential to induce sterical clash, which might be considered a reason for protein misfolding. hGly422 is conserved among ALOX5, ALOX12 and ALOX15 isoforms and corresponding hALOX12 and hALOX5 mutants also exhibited a reduced catalytic activity. Interestingly, in the hALOX5 Gly429Glu mutants the reaction specificity of arachidonic acid oxygenation was shifted from 5S- to 8S- and 12R-H(p)ETE formation. Taken together, our data indicate that the conserved glycine is of functional importance for these enzyme variants and most mutants at this position lose catalytic activity.

• Authors: Thomas Horn, Igor Ivanov, Almerinda Di Venere, Kumar Reddy Kakularam, Pallu Reddanna, Melanie L Conrad, Constanze Richter, Patrick Scheerer, Hartmut Kuhn
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1831 Issue 12 Pg. 1702-13 (Dec 2013) ISSN: 0006-3002 [Print] Netherlands
• PMID: 23958500 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2013.

Chemical References

• Hydroxyeicosatetraenoic Acids
• Isoenzymes
• Recombinant Proteins
• Glutamine
• ALOX15 protein, human
• Arachidonate 15-Lipoxygenase
• Glycine

Topics

• Amino Acid Sequence
• Animals
• Arachidonate 15-Lipoxygenase (chemistry, genetics, metabolism)
• Catalytic Domain
• Conserved Sequence
• Enzyme Stability
• Escherichia coli (genetics, metabolism)
• Glutamine (chemistry, genetics)
• Glycine (chemistry, genetics)
• Humans
• Hydroxyeicosatetraenoic Acids (chemistry, metabolism)
• Isoenzymes (chemistry, genetics, metabolism)
• Kinetics
• Models, Molecular
• Molecular Sequence Data
• Mutation
• Protein Folding
• Rabbits
• Recombinant Proteins (chemistry, genetics, metabolism)
• Sequence Homology, Amino Acid
• Thermodynamics