X-Message-Number: 9704
Date: Wed, 13 May 1998 05:12:48 -0700 (PDT)
From: Doug Skrecky <>
Subject: arbutin & anhydrobiosis

Authors
  Oliver AE.  Crowe LM.  de Araujo PS.  Fisk E.  Crowe JH.
Institution
  Section of Molecular and Cellular Biology, University of California, Davis
  95616, USA. aeoliver:ucdavis.edu
Title
  Arbutin inhibits PLA2 in partially hydrated model systems.
Source
  Biochimica et Biophysica Acta.  1302(1):69-78, 1996 Jul 12.
Abstract
  Arbutin is a glycosylated hydroquinone found at high concentrations in
  certain plants capable of surviving extreme and sustained dehydration. In
  this paper, we examine a potential role of this molecule in
  anhydrobiosis. We have studied its effects on the physical
  properties of phospholipids and on preservation of liposomes during drying.
  Arbutin depresses the gel to liquid crystalline phase transition temperature
  of dry phospholipids, as measured by differential scanning calorimetry, with
  a pattern similar to that seen in phospholipids dried with the disaccharide
  trehalose. Unlike trehalose, however, arbutin does not protect dry liposomes
  from leaking their contents. Also, using Fourier transform infrared
  spectroscopy, we found an increase in the vibrational frequency of the
  phosphate asymmetric stretch in partially hydrated phospholipids in the
  presence of arbutin. Trehalose, by contrast, depresses the frequency of the
  phosphate in dry phospholipids, indicating that the modes of interaction of
  trehalose and arbutin with the bilayer are different. Previously, we have
  shown that phospholipases can be active in liposomes with surprisingly low
  water contents. Based on the structural similarity of arbutin to a known
  inhibitor of phospholipase A2 (PLA2), it appeared possible that arbutin might
  serve as an inhibitor of phospholipases. Liposomes of varying composition
  were lyophilized in the presence and absence of phospholipases. When the
  liposomes were partially rehydrated at 76% relative humidity, arbutin
  inhibited PLA2, but did not inhibit phospholipases B or C. Accumulation of
  enzyme product in the liposome membranes was measured by analytical thin
  layer chromatography, and was taken as a measure of enzyme activity. Arbutin
  did not inhibit any of the enzymes in the presence of excess water. Based on
  these data, hypotheses are presented concerning the mechanism of PLA2
  inhibition by arbutin in the mostly dehydrated state.

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