Subcellular distribution and characteristics of trihydroxycoprostanoyl-CoA synthetase in rat liver.
The subcellular distribution and characteristics of trihydroxycoprostanoyl-CoA synthetase were studied in rat liver and were compared with those of palmitoyl-CoA synthetase and choloyl-CoA synthetase. Trihydroxycoprostanoyl-CoA synthetase and choloyl-CoA synthetase were localized almost completely in the endoplasmic reticulum. A quantitatively insignificant part of trihydroxycoprostanoyl-CoA synthetase was perhaps present in mitochondria. Peroxisomes, which convert trihydroxycoprostanoyl-CoA into choloyl-CoA, were devoid of trihydroxycoprostanoyl-CoA synthetase. As already known, palmitoyl-CoA synthetase was distributed among mitochondria, peroxisomes and endoplasmic reticulum. Substrate- and cofactor- (ATP, CoASH) dependence of the three synthesis activities were also studied. Cholic acid and trihydroxycoprostanic acid did not inhibit palmitoyl-CoA synthetase; palmitate inhibited the other synthetases non-competitively. Likewise, cholic acid inhibited trihydroxycoprostanic acid activation non-competitively and vice versa. The pH curves of the synthetases did not coincide. Triton X-100 affected the activity of each of the synthetases differently. Trihydroxycoprostanoyl-CoA synthetase was less sensitive towards inhibition by pyrophosphate than choloyl-CoA synthetase. The synthetases could not be solubilized from microsomal membranes by treatment with 1 M-NaCl, but could be solubilized with Triton X-100 or Triton X-100 plus NaCl. The detergent-solubilized trihydroxycoprostanoyl-CoA synthetase could be separated from the solubilized choloyl-CoA synthetase and palmitoyl-CoA synthetase by affinity chromatograpy on Sepharose to which trihydroxycoprostanic acid was bound. Choloyl-CoA synthetase and trihydroxycoprostanoyl-CoA synthetase could not be detected in homogenates from kidney or intestinal mucosa. The results indicate that long-chain fatty acids, cholic acid and trihydroxycoprostanic acid are activated by three separate enzymes.
Schepers
L
L
Afdeling Farmacologie, Katholieke Universiteit Leuven, Belgium.
Casteels
M
M
Verheyden
K
K
Parmentier
G
G
Asselberghs
S
S
Eyssen
H J
HJ
Mannaerts
G P
GP
D000818:Animals; D003066:Coenzyme A Ligases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D008099:Liver / Q000201:enzymology* / Q000648:ultrastructure; D008830:Microbodies / Q000201:enzymology; D008861:Microsomes / Q000201:enzymology; D008930:Mitochondria, Liver / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D000098859:Long-Chain-Fatty-Acid-CoA Ligase
D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D003066:Coenzyme A Ligases; C058701:trihydroxycoprostanoyl coenzyme A synthetase; C090799:FAA2 protein, S cerevisiae; D000098859:Long-Chain-Fatty-Acid-CoA Ligase; C019890:choloyl-CoA synthetase