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J Gen Physiol. 2019 Feb 4;151(2):258-263. doi: 10.1085/jgp.201812260. Epub 2019 Jan 8.

Reinterpretation of the substrate specificity of the voltage-sensing phosphatase during dimerization.

Author information

1
Department of Biology and Program in Neuroscience, Bates College, Lewiston, ME.
2
Department of Cell Biology and Neuroscience, Montana State University, Bozeman, MT.
3
Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA hille@uw.edu.

Abstract

Voltage-sensing phosphatases (VSPs) cleave both 3- and 5-phosphates from inositol phospholipids in response to membrane depolarization. When low concentrations of Ciona intestinalis VSP are expressed in Xenopus laevis oocytes, the 5-phosphatase reaction can be observed during large membrane depolarizations. When higher concentrations are expressed, the 5-phosphatase activity is observed with smaller depolarizations, and the 3-phosphatase activity is revealed with strong depolarization. Here we ask whether this apparent induction of 3-phosphatase activity is attributable to the dimerization that has been reported when VSP is expressed at higher concentrations. Using a simple kinetic model, we show that these enzymatic phenomena can be understood as an emergent property of a voltage-dependent enzyme with invariant substrate selectivity operating in the context of endogenous lipid-metabolizing enzymes present in oocytes. Thus, a switch of substrate specificity with dimerization need not be invoked to explain the appearance of 3-phosphatase activity at high VSP concentrations.

PMID:
30622132
PMCID:
PMC6363406
[Available on 2019-08-04]
DOI:
10.1085/jgp.201812260

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