Possible Roles of Long-chain Fatty Acyl-CoA Esters in the Fusion of Biomembranes - Fusion of Biological Membranes and Related Problems - page 205

microcalorimetry, the K D values for palmitoyl-CoA binding to bovine, yeast,
and rat ACBP were determined to 2.0,2.3, and 8.9nM, respectively (Fulceri
et al., 1997). Results from a number of in vitro and in vivo experimental
results strongly indicate that ACBP is able to act as an intracellular acyl-
CoA transporter and pool former. In vitro, ACBP has a strong attenuating
effect on the inhibition of acetyl-coA carboxylase and on the mitochon-
drial adenine nucleotide translocase by LCACoA (Rasmussen et al., 1993),
it readily prevent membrane binding and insertion and protect acyl-CoA
against hydrolysis by microsomal hydrolases and stimulate the mitochon-
drial LCACoA synthetase (Rasmussen et al., 1993). Over expressing of
either bovine or yeast ACBP in Saccharomyces cerevisiae led to an
increased intracellular acyl-CoA level indicating that ACBP is able to act
as an acyl-CoA pool former in vivo (Knudsen et al., 1994; Mandrup et al.,
1993). ACBP is able to desorb acyl-CoA esters immobilized in multilamel-
lar liposomes on a nitrocellulose membrane, and transport and donate these
to -oxidation and to microsomal glycerolipid synthesis

(Rasmussen et al., 1994). Compelling evidence that ACBP participates in
acyl-CoA transport in vivo has been obtained from yeast. Disruption of the
ACBP-gene in Saccharomyces cerevisiae results in a dramatic perturbation
of the acyl-CoA level and composition (Scherling et al., 1996). The level of
total acyl-CoA and stearoyl-CoA was increased 2.5 and 7.0 fold respec-
tively. Despite of that, the

mitochondrial β

-9 desaturase mRNA level in the ACBP knock-
out strain was increased 3-fold, no change in the synthesis of
monounsaturated fatty acids or the overall fatty acid composition in the
knock out strain could be observed. These results strongly suggest that the
increased stearoyl-CoA pool in the ACBP knock-out strain was not avail-
able for the

δ

-9 desaturase and that the ACBP knock out strain has a defect
in intracellular acyl-CoA transport.

δ

7.2. Fatty Acid Binding Protein and Sterol Carrier Protein-2 in
Acyl-CoA Metabolism

Ever since it was noted that fatty acid binding proteins (FABPs) are
capable of binding acyl-CoA esters with appreciable affinity (Mishkin and
Turcotte, 1974a; Ketterer et al., 1976) FABPs have been suggested to play
an important role in acyl-CoA metabolism. FABPs constitute a family of
proteins with a molecular mass of 14-15 kDa, which are abundantly present
in the cytoplasm of tissues that are involved in the uptake or utilization of
fatty acids. All FABP types bind long-chain fatty acids with K D -values
ranging from 10 nM to 1.0µM. (Frolov et al., 1997; Rolf et al., 1995; Paulussen
et al., 1988; Burrier et al., 1987; Ketterer et al., 1976; Mishkin and Turcotte,
1974a). The binding stoichiometry is one mole ligand per mole protein