Publications

• Bile acid sulfotransferase I from rat liver sulfates bile acids and 3-hydroxy steroids: purification, N-terminal amino acid sequence, and kinetic properties.

  Barnes S., Buchina E.S., King R.J., McBurnett T., Taylor K.B.

  A bile acid:3'phosphoadenosine-5'phosphosulfate:sulfotransferase (BAST I) from adult female rat liver cytosol has been purified 157-fold by a two-step isolation procedure. The N-terminal amino acid sequence of the 30,000 subunit has been determined for the first 35 residues. The Vmax of purified B ... >> More

  A bile acid:3'phosphoadenosine-5'phosphosulfate:sulfotransferase (BAST I) from adult female rat liver cytosol has been purified 157-fold by a two-step isolation procedure. The N-terminal amino acid sequence of the 30,000 subunit has been determined for the first 35 residues. The Vmax of purified BAST I is 18.7 nmol/min per mg protein with N-(3-hydroxy-5 beta-cholanoyl)glycine (glycolithocholic acid) as substrate, comparable to that of the corresponding purified human BAST (Chen, L-J., and I. H. Segel, 1985. Arch. Biochem. Biophys. 241: 371-379). BAST I activity has a broad pH optimum from 5.5-7.5. Although maximum activity occurs with 5 mM MgCl2, Mg2+ is not essential for BAST I activity. The greatest sulfotransferase activity and the highest substrate affinity is observed with bile acids or steroids that have a steroid nucleus containing a 3 beta-hydroxy group and a 5-6 double bond or a trans A-B ring junction. These substrates have normal hyperbolic initial velocity curves with substrate inhibition occurring above 5 microM. Of the saturated 5 beta-bile acids, those with a single 3-hydroxy group are the most active. The addition of a second hydroxy group at the 6- or 7-position eliminates more than 99% of the activity. In contrast, 3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid (deoxycholic acid) is an excellent substrate. The initial velocity curves for glycolithocholic and deoxycholic acid conjugates are sigmoidal rather than hyperbolic, suggestive of an allosteric effect. Maximum activity is observed at 80 microM for glycolithocholic acid. All substrates, bile acids and steroids, are inhibited by the 5 beta-bile acid, 3-keto-5 beta-cholanoic acid. The data suggest that BAST I is the same protein as hydrosteroid sulfotransferase 2 (Marcus, C. J., et al. 1980. Anal. Biochem. 107: 296-304). << Less

  J. Lipid Res. 30:529-540(1989) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• The enzymes, regulation, and genetics of bile acid synthesis.

  Russell D.W.

  The synthesis and excretion of bile acids comprise the major pathway of cholesterol catabolism in mammals. Synthesis provides a direct means of converting cholesterol, which is both hydrophobic and insoluble, into a water-soluble and readily excreted molecule, the bile acid. The biosynthetic steps ... >> More

  The synthesis and excretion of bile acids comprise the major pathway of cholesterol catabolism in mammals. Synthesis provides a direct means of converting cholesterol, which is both hydrophobic and insoluble, into a water-soluble and readily excreted molecule, the bile acid. The biosynthetic steps that accomplish this transformation also confer detergent properties to the bile acid, which are exploited by the body to facilitate the secretion of cholesterol from the liver. This role in the elimination of cholesterol is counterbalanced by the ability of bile acids to solubilize dietary cholesterol and essential nutrients and to promote their delivery to the liver. The synthesis of a full complement of bile acids requires 17 enzymes. The expression of selected enzymes in the pathway is tightly regulated by nuclear hormone receptors and other transcription factors, which ensure a constant supply of bile acids in an ever changing metabolic environment. Inherited mutations that impair bile acid synthesis cause a spectrum of human disease; this ranges from liver failure in early childhood to progressive neuropathy in adults. << Less

  Annu. Rev. Biochem. 72:137-174(2003) [PubMed] [EuropePMC]

  This publication is cited by 13 other entries.

• Evidence for an ordered reaction mechanism for bile salt: 3'phosphoadenosine-5'-phosphosulfate: sulfotransferase from rhesus monkey liver that catalyzes the sulfation of the hepatotoxin glycolithocholate.

  Barnes S., Waldrop R., Crenshaw J., King R.J., Taylor K.B.

  The in vivo formation of the sulfate ester of glycolithocholate is a critical step in the elimination of this hepatotoxic bile salt. Rhesus monkeys fed chenodeoxycholate or ursodeoxycholate, the precursors of lithocholate, develop frank cirrhosis in association with accumulation of nonsulfated gly ... >> More

  The in vivo formation of the sulfate ester of glycolithocholate is a critical step in the elimination of this hepatotoxic bile salt. Rhesus monkeys fed chenodeoxycholate or ursodeoxycholate, the precursors of lithocholate, develop frank cirrhosis in association with accumulation of nonsulfated glycolithocholate in bile. An enzyme catalyzing the formation of glycolithocholate-3-sulfate has been isolated from hepatic cytosol of adult female rhesus monkeys and has been purified 146-fold. When reduced it appears as a 30 kD band on an SDS-polyacrylamide gradient gel. It has a pH optimum of 7.0 and is stimulated by low concentrations of Mg2+ (up to 2 mM), but does not have an absolute requirement for this metal ion. The kinetics of this enzyme have been investigated to ascertain whether its reaction mechanism can account for the poor in vivo rate of glycolithocholate sulfation. Inhibitor studies with an oxidized metabolite of lithocholate, 3-keto-5 beta-cholanoate, showed that the latter is a competitive inhibitor of glycolithocholate and is noncompetitive with the active form of sulfate, 3'phosphoadenosine-5'-phosphosulfate. The monophosphonucleotide 3'-AMP is a competitive inhibitor of 3'phosphoadenosine-5'-phosphosulfate, and is noncompetitive with glycolithocholate. These observations are consistent with a sequentially ordered Bi Bi reaction mechanism in which the bile salt is the first substrate to bind to the enzyme. Such a reaction mechanism for bile salt:3'phosphoadenosine-5'-phosphosulfate:sulfotransferase would be, therefore, the first time in which the sulfate acceptor (the bile salt) is the initial substrate to bind to a sulfotransferase. These studies have shown that although rhesus monkeys have a liver enzyme capable of forming the sulfate ester of glycolithocholate, its reaction mechanism and the potent inhibition caused by simple metabolites, such as 3-keto-5 beta-cholanoate, may serve to under-express the activity of the enzyme in vivo. << Less

  J Lipid Res 27:1111-1123(1986) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.