Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.2.1.7 (BAL)
 1,977 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Liver peroxisomes from both rat and humans have previously been shown to contain enzymes that catalyze the oxidative cleavage of the C27-steroid side chain in the formation of bile acids. It has not been clear, however, whether the initial step, formation of the CoA-esters of the 5 beta-cholestanoic acids, also occurs in these organelles. In the present work the subcellular localization of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoyl-CoA (THCA-CoA) ligase (THCA-CoA synthetase) and of 3 alpha,7 alpha-dihydroxy-5 beta-cholestanoyl-CoA (DHCA-CoA) ligase in rat liver has been investigated. Main subcellular fractions and peroxisome-rich density gradient fractions from rat liver were incubated with THCA or DHCA, CoA, ATP, and Mg2+. Formation of THCA-CoA and DHCA-CoA was determined after high pressure liquid chromatography of the incubation extracts. The microsomal fraction contained the highest specific (and also relative specific) activity both for the formation of THCA-CoA and DHCA-CoA. The rates of THCA-CoA formation were further increased from 124-159 nmol/mg.hr-1 in crude microsomal fractions to 184-220 nmol/mg.hr-1 when studied in purified rough endoplasmic reticulum fractions. Formation of THCA-CoA in peroxisomal fractions prepared in Nycodenz density gradients could be accounted for by a small contamination (3-7%) by microsomal protein. The distribution of THCA-CoA ligase was different from that of palmitoyl-CoA ligase that was found to be localized also to the peroxisomal fractions.
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PMID:Subcellular localization of 3 alpha, 7 alpha-dihydroxy- and 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoyl-coenzyme A ligase(s) in rat liver. 318 23

We have examined the ability of HepG2 human hepatoblastoma cells and 7800 C1 Morris rat hepatoma cells to convert 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA) and 3 alpha, 7 alpha-dihydroxy-5 beta-cholestanoic acid (DHCA) to cholic acid and chenodeoxycholic acid, respectively. Cell extracts from both these cell lines could neither form cholic acid from THCA nor from the activated form, THCA-CoA. This suggests that both cell lines are defective in two enzyme activities involved in the pathway, the microsomal THCA-CoA ligase and the peroxisomal THCA-CoA oxidase. Furthermore, we show that the subsequent enzymes are active in the conversion to bile acids, because the product of the THCA-CoA oxidase, 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholest-24-enoyl-coenzyme A (delta 24-THCA-CoA) or delta 24-THCA in the presence of THCA-CoA ligase, are converted to cholic acid by both cell lines. HepG2 cells were able to slowly form chenodeoxycholic acid and cholic acid from 5 beta-cholestane-3 alpha, 7 alpha-diol and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol, respectively, in 24- and 96-h incubations. The rate of cholic acid formation was lower than the rate for chenodeoxycholic acid and there was a clear accumulation of THCA. 7800 C1 Morris cells had no ability to form cholic acid or chenodeoxycholic acid after 96 h incubation. We conclude that these two cell lines have defects in two enzyme activities involved in the peroxisomal oxidation in bile acid formation, the microsomal THCA-CoA ligase and the peroxisomal THCA-CoA oxidase.
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PMID:Human hepatoblastoma cells (HepG2) and rat hepatoma cells are defective in important enzyme activities in the oxidation of the C27 steroid side chain in bile acid formation. 830 Dec 25