TY - JOUR
T1 - 2-Fluoro-β-alanine, a previously unrecognized substrate for bile acid coenzyme A:Amino acid:N-acyltransferase from human liver
AU - Johnson, Martin R.
AU - Barnes, Stephen
AU - Sweeny, David J.
AU - Diasio, Robert B.
N1 - Funding Information:
Aek~wZedgeme~~-We thank Dr. John Baker and Ms. Kelly Morrison for their assistancein analyzingt he purity of the FBAL and Dr. Seng-JawS oongf or his assistancein analyzingt he kinetic data. We also wish to thank Mrs. BeverlyC averf or her excellents ecretariaal ssistanceT. his work was supportedb y USPHS GrantC A-40530.
PY - 1990/9/15
Y1 - 1990/9/15
N2 - Our laboratory has demonstrated recently that conjugates of 2-fluoro-β-alanine (FBAL) and bile acids are the major biliary metabolites of 5-fluorouracil (FUra) in cancer patients. Bile acids are normally conjugated with glycine or taurine, and therefore the identification of the FBAL-bile acid conjugates suggested that FBAL may also be a substrate for the bile acid conjugating enzyme, bile acid CoA : amino acid : N-acyltransferase. Enzyme activity detected using glycine and taurine as substrates was purified 8-fold from human liver cytosol using a DEAE-cellulose column. This preparation when tested for its activity towards β-alanine and FBAL using cholyl CoA as the bile acid substrate only catalyzed the formation of FBAL-cholate. β-Alanine was not a substrate. Confirmation of FBAL-cholate as the enzymatic product was demonstrated by (1) coelution of the product of this reaction on HPLC with authentic FBAL-cholate, (2) specific hydrolysis of this product by cholylglycine hydrolase, and (3) molecular weight of the product (497) being identical to that of the authentic FBAL-cholate. Kinetic experiments demonstrated that the enzyme had an affinity for FBAL (Km 1.45 mM) comparable to taurine (Km 1.32 mM), but greater than glycine (Km, 6.45 mM). Formation of FBAL-cholate was inhibited competitively by taurine (Ki 1.27 mM) and glycine (Ki 4.47 mM), suggesting that a single enzyme is responsible for conjugation of glycine, taurine and FBAL with bile acids. These data indicate that the formation of the FBAL-bile acid conjugates in patients receiving FUra results from high affinity of the bile acid conjugating enzyme for FBAL.
AB - Our laboratory has demonstrated recently that conjugates of 2-fluoro-β-alanine (FBAL) and bile acids are the major biliary metabolites of 5-fluorouracil (FUra) in cancer patients. Bile acids are normally conjugated with glycine or taurine, and therefore the identification of the FBAL-bile acid conjugates suggested that FBAL may also be a substrate for the bile acid conjugating enzyme, bile acid CoA : amino acid : N-acyltransferase. Enzyme activity detected using glycine and taurine as substrates was purified 8-fold from human liver cytosol using a DEAE-cellulose column. This preparation when tested for its activity towards β-alanine and FBAL using cholyl CoA as the bile acid substrate only catalyzed the formation of FBAL-cholate. β-Alanine was not a substrate. Confirmation of FBAL-cholate as the enzymatic product was demonstrated by (1) coelution of the product of this reaction on HPLC with authentic FBAL-cholate, (2) specific hydrolysis of this product by cholylglycine hydrolase, and (3) molecular weight of the product (497) being identical to that of the authentic FBAL-cholate. Kinetic experiments demonstrated that the enzyme had an affinity for FBAL (Km 1.45 mM) comparable to taurine (Km 1.32 mM), but greater than glycine (Km, 6.45 mM). Formation of FBAL-cholate was inhibited competitively by taurine (Ki 1.27 mM) and glycine (Ki 4.47 mM), suggesting that a single enzyme is responsible for conjugation of glycine, taurine and FBAL with bile acids. These data indicate that the formation of the FBAL-bile acid conjugates in patients receiving FUra results from high affinity of the bile acid conjugating enzyme for FBAL.
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U2 - 10.1016/0006-2952(90)90389-3
DO - 10.1016/0006-2952(90)90389-3
M3 - Article
C2 - 2119585
AN - SCOPUS:0025151029
SN - 0006-2952
VL - 40
SP - 1241
EP - 1246
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 6
ER -