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Related Experiment Video

Updated: Jun 25, 2026

siRNA Electroporation to Modulate Autophagy in Herpes Simplex Virus Type 1-Infected Monocyte-Derived Dendritic Cells

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Novel point mutations attenuate autotaxin activity.

Eunjin Koh¹, Russell W Bandle, David D Roberts

¹Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1500, USA. ek4a@virginia.edu

Lipids in Health and Disease

|February 19, 2009

Summary

Autotaxin (ATX) mutations H226Q and H434Q impair its ability to hydrolyze artificial substrates more than lysophospholipids. These findings are crucial for understanding ATX regulation and developing accurate diagnostic assays.

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Published on: March 27, 2020

Area of Science:

Biochemistry
Enzymology
Molecular Biology

Background:

Autotaxin (ATX) is a secreted enzyme that promotes tumor progression by producing lysophosphatidic acid (LPA).
Regulation of ATX activity, particularly its substrate interactions, is poorly understood.
Unexpectedly low plasma LPA concentrations suggest ATX activity is tightly regulated.

Purpose of the Study:

To investigate the hydrolytic activities of ATX toward various substrates.
To characterize the impact of specific ATX mutations on enzyme function.
To understand the role of ATX active site residues in substrate binding and catalysis.

Main Methods:

Enzyme kinetics assays using artificial substrates (pNpTMP, FS-3) and natural substrates (lysophospholipids).
Site-directed mutagenesis to create H226Q, H434Q, and H420Q ATX variants.
Cell migration assays to assess the biological activity of wild-type (WT) and mutant ATX.

Main Results:

Mutations H226Q and H434Q significantly reduced ATX activity toward artificial substrates but had a less pronounced effect on lysophospholipid hydrolysis.
The Vmax for lysophospholipid hydrolysis varied with chain length and saturation, independent of mutations.
Mutant ATX forms showed reduced tumor cell migration, which could be rescued by exogenous lysophospholipids.

Conclusions:

H226Q-ATX and H434Q-ATX are the first ATX/NPP2 mutants exhibiting differential substrate hydrolysis, with a disproportionate decrease in activity against artificial substrates.
Histidine residues at positions 226 and 434 are critical for ATX interaction with certain substrates.
Assays relying on artificial substrates may misinterpret the activity of ATX variants that can still produce LPA in vivo.