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Dependence of the activity of phospholipase C beta on surface pressure and surface composition in phospholipid monolayers and its implications for their regulation.
Biochemistry. 1997 Jan 28; 36(4):848-55.B

Abstract

We have examined the influence of surface pressure and phospholipid composition on hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP2) by phospholipase C beta 1 (PLC beta 1) and PLC beta 2 in mixed composition phospholipid monolayers. Increasing the monolayer surface pressure from 15 to 36 mN/m reduced the rate at which PIP2 was hydrolyzed by PLC beta 1 and PLC beta 2 by 4-6-fold, although PLC beta 1 was more active than PLC beta 2, even at high surface pressure. Reduced enzyme activity was accompanied by an increase in reaction induction times, suggesting that increasing surface pressure reduced the penetration rate of the enzymes into the monolayer. Quantitation of interfacial enzyme concentration using 35S-labeled PLC beta 1 confirmed that less enzyme was associated with the monolayer at higher pressures. The relationship between PLC activity and substrate concentration was examined at a single surface pressure of 30 mN/m. This relationship was not hyperbolic, and increases in the mole percentage (mol %) of PIP2 in the monolayer resulted in an upwardly-curving increase in PLC activity. Thus, PLC beta 1 activity increased 7-fold and PLC beta 2 activity increased 4-fold when the mol % of PIP2 in the monolayer increased from 17.9% to 29%, increasing further thereafter. Paradoxically, increasing the mol % of PIP2 from 0 to 60% was accompanied by a 3-fold decrease in interfacial enzyme concentrations. Taken together, these data show that the catalytic activity of PLC beta involves some element of penetration of lipid interfaces, and suggest that the organization of the substrate facilitates PLC activity, giving credence to the substrate theory of interfacial activation of phospholipases. We present a hypothesis suggesting that PIP2 molecules coalesce into enriched lateral domains which favor PLC beta activity.

Authors+Show Affiliations

Department of Biochemistry, University of Dundee, Scotland, U.K. srjames@bad.dundee.ac.ukNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9020783

Citation

James, S R., et al. "Dependence of the Activity of Phospholipase C Beta On Surface Pressure and Surface Composition in Phospholipid Monolayers and Its Implications for Their Regulation." Biochemistry, vol. 36, no. 4, 1997, pp. 848-55.
James SR, Paterson A, Harden TK, et al. Dependence of the activity of phospholipase C beta on surface pressure and surface composition in phospholipid monolayers and its implications for their regulation. Biochemistry. 1997;36(4):848-55.
James, S. R., Paterson, A., Harden, T. K., Demel, R. A., & Downes, C. P. (1997). Dependence of the activity of phospholipase C beta on surface pressure and surface composition in phospholipid monolayers and its implications for their regulation. Biochemistry, 36(4), 848-55.
James SR, et al. Dependence of the Activity of Phospholipase C Beta On Surface Pressure and Surface Composition in Phospholipid Monolayers and Its Implications for Their Regulation. Biochemistry. 1997 Jan 28;36(4):848-55. PubMed PMID: 9020783.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Dependence of the activity of phospholipase C beta on surface pressure and surface composition in phospholipid monolayers and its implications for their regulation. AU - James,S R, AU - Paterson,A, AU - Harden,T K, AU - Demel,R A, AU - Downes,C P, PY - 1997/1/28/pubmed PY - 1997/1/28/medline PY - 1997/1/28/entrez SP - 848 EP - 55 JF - Biochemistry JO - Biochemistry VL - 36 IS - 4 N2 - We have examined the influence of surface pressure and phospholipid composition on hydrolysis of phosphatidylinositol (4,5)-bisphosphate (PIP2) by phospholipase C beta 1 (PLC beta 1) and PLC beta 2 in mixed composition phospholipid monolayers. Increasing the monolayer surface pressure from 15 to 36 mN/m reduced the rate at which PIP2 was hydrolyzed by PLC beta 1 and PLC beta 2 by 4-6-fold, although PLC beta 1 was more active than PLC beta 2, even at high surface pressure. Reduced enzyme activity was accompanied by an increase in reaction induction times, suggesting that increasing surface pressure reduced the penetration rate of the enzymes into the monolayer. Quantitation of interfacial enzyme concentration using 35S-labeled PLC beta 1 confirmed that less enzyme was associated with the monolayer at higher pressures. The relationship between PLC activity and substrate concentration was examined at a single surface pressure of 30 mN/m. This relationship was not hyperbolic, and increases in the mole percentage (mol %) of PIP2 in the monolayer resulted in an upwardly-curving increase in PLC activity. Thus, PLC beta 1 activity increased 7-fold and PLC beta 2 activity increased 4-fold when the mol % of PIP2 in the monolayer increased from 17.9% to 29%, increasing further thereafter. Paradoxically, increasing the mol % of PIP2 from 0 to 60% was accompanied by a 3-fold decrease in interfacial enzyme concentrations. Taken together, these data show that the catalytic activity of PLC beta involves some element of penetration of lipid interfaces, and suggest that the organization of the substrate facilitates PLC activity, giving credence to the substrate theory of interfacial activation of phospholipases. We present a hypothesis suggesting that PIP2 molecules coalesce into enriched lateral domains which favor PLC beta activity. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/9020783/Dependence_of_the_activity_of_phospholipase_C_beta_on_surface_pressure_and_surface_composition_in_phospholipid_monolayers_and_its_implications_for_their_regulation_ L2 - https://dx.doi.org/10.1021/bi962108q DB - PRIME DP - Unbound Medicine ER -