Journal of Lipid Research, Vol 25, 1222-1232, Copyright © 1984 by Lipid Research, Inc.
Localization and characterization of the sn-glycerol-3-phosphate acyltransferase in Rhodopseudomonas sphaeroides
CL Cooper and DR Lueking
The membrane localization and properties of the Rhodopseudomonas
sphaeroides sn-glycerol-3-phosphate acyltransferase have been examined
utilizing enzymatically prepared acyl-acyl carrier protein (acyl-ACP)
substrates as acyl donors for sn-glycerol-3-phosphate acylation. Studies
conducted with membranes prepared from chemotrophically and
phototrophically grown cells show that sn-glycerol-3-phosphate
acyltransferase activity is predominantly (greater than 80%) associated
with the cell's cytoplasmic membrane. Enzyme activity associated with the
intracytoplasmic membranes present in phototrophically grown R. sphaeroides
was within the range attributable to cytoplasmic membrane contamination of
this membrane fraction. Enzyme activity was optimal at 40 degrees C and pH
7.0 to 7.5, and required the presence of magnesium. No enzyme activity was
observed with any of the long-chain acyl-CoA substrates examined.
Vaccenoyl-ACP was the preferred acyl-ACP substrate and vaccenoyl-ACP and
palmitoyl-ACP were independently utilized to produce lysophosphatidic and
phosphatidic acids. With either vaccenoyl- ACP or palmitoyl-ACP as sole
acyl donor substrate, the lysophosphatidic acid formed was primarily
1-acylglycerol-3-phosphate and the Km(app) for sn-glycerol-3-phosphate
utilization was 96 microM. The implications of these results to the mode
and regulation of phospholipid synthesis in R. sphaeroides are discussed.
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