TY - JOUR
T1 - The Catalytic Effect of Bovine Serum Albumin on the Ortho Rearrangement of the Potential Ultimate Carcinogen, N-(Sulfooxy)-2-(acetylamino)fluorene, Generated Enzymatically from N-Hydroxy-2-(acetylamino)fluorene and Evidence for Substrate Specificity of the Enzymatic Sulfonation of Arylhydroxamic Acids
AU - Kolanczyk, Richard C.
AU - Rutks, Indulis R.
AU - Gutmann, Helmut R.
N1 - Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 1991/3/1
Y1 - 1991/3/1
N2 - This investigation examines the catalytic effect of bovine serum albumin on the ortho rearrangement of the possible ultimate carcinogen, N-(sulfooxy)-2-(acetylamino)fluorene, generated from N-hydroxy-2-(acetylamino)fluorene by the sulfotransferase(s) in the cytosol of rat liver. With various preparations of cytosol, 55–75% of the substrate, N-hydroxy-2-(acetylamino)-fluorene, was found to rearrange to the nonmutagenic and noncarcinogenic o-(sulfooxy) esters, 1- and 3-(sulfooxy)-2-(acetylamino)fluorene, in the presence of bovine serum albumin, while <1% of the substrate rearranged in its absence. In presence of bovine serum albumin the cytosolic reduction of N-(sulfooxy)-2-(acetylamino)fluorene to 2-(acetylamino)fluorene decreased by 60–90% and its solvolytic degradation to 4-hydroxy-2-(acetylamino)fluorene by 80–90%. The covalent interaction of enzymatically generated N-(sulfooxy)-2-(acetylamino)fluorene with the nucleophilic acceptors, N-acetyl-l-methionine and guanosine, was lowered by >90% by addition of bovine serum albumin. These measurements indicated that the albumin-catalyzed ortho rearrangement controls the rates of concurrent metabolic and degradative reactions of N-(sulfooxy)-2-(acetylamino)fluorene. The results are in agreement with previous findings of a catalytic effect of serum albumin on the ortho rearrangement of synthetic N-(sulfooxy)-2-(acetylamino)fluorene. In contrast to its catalytic effect on the formation of o-(sulfooxy) esters from N-(sulfooxy)-2-(acetylamino)fluorene, bovine serum albumin had no effect on the formation of o-(acetylamino)fluorenols. To assess the substrate specificity of bovine serum albumin, its effect on the rearrangement of N-hydroxy-2-(benzoylamino)fluorene, a carcinogenic analogue of N-hydroxy-2-(acetylamino)fluorene, was analyzed under conditions of cytosolic sulfonation. Bovine serum albumin did not significantly increase the minimal quantities of the o-(sulfooxy) esters of 1- and 3-hydroxy-2-(benzoylamino)fluorene formed in its absence. However, synthetic sulfonation of N-hydroxy-2-(benzoylamino)fluorene yielded major amounts (85%) of the o-(sulfooxy) esters. These findings indicate that N-(sulfooxy)-2-(benzoylamino)fluorene is unstable and undergoes rapid ortho rearrangement. The evidence suggests that N-hydroxy-2-(benzoylamino)fluorene is a poor substrate for cytosolic sulfonation. It is therefore not a substrate suitable for investigation of the specificity of bovine serum albumin in catalyzing the ortho arrangement of enzymatically generated N-(sulfooxy) esters of arylhydroxyamic acids.
AB - This investigation examines the catalytic effect of bovine serum albumin on the ortho rearrangement of the possible ultimate carcinogen, N-(sulfooxy)-2-(acetylamino)fluorene, generated from N-hydroxy-2-(acetylamino)fluorene by the sulfotransferase(s) in the cytosol of rat liver. With various preparations of cytosol, 55–75% of the substrate, N-hydroxy-2-(acetylamino)-fluorene, was found to rearrange to the nonmutagenic and noncarcinogenic o-(sulfooxy) esters, 1- and 3-(sulfooxy)-2-(acetylamino)fluorene, in the presence of bovine serum albumin, while <1% of the substrate rearranged in its absence. In presence of bovine serum albumin the cytosolic reduction of N-(sulfooxy)-2-(acetylamino)fluorene to 2-(acetylamino)fluorene decreased by 60–90% and its solvolytic degradation to 4-hydroxy-2-(acetylamino)fluorene by 80–90%. The covalent interaction of enzymatically generated N-(sulfooxy)-2-(acetylamino)fluorene with the nucleophilic acceptors, N-acetyl-l-methionine and guanosine, was lowered by >90% by addition of bovine serum albumin. These measurements indicated that the albumin-catalyzed ortho rearrangement controls the rates of concurrent metabolic and degradative reactions of N-(sulfooxy)-2-(acetylamino)fluorene. The results are in agreement with previous findings of a catalytic effect of serum albumin on the ortho rearrangement of synthetic N-(sulfooxy)-2-(acetylamino)fluorene. In contrast to its catalytic effect on the formation of o-(sulfooxy) esters from N-(sulfooxy)-2-(acetylamino)fluorene, bovine serum albumin had no effect on the formation of o-(acetylamino)fluorenols. To assess the substrate specificity of bovine serum albumin, its effect on the rearrangement of N-hydroxy-2-(benzoylamino)fluorene, a carcinogenic analogue of N-hydroxy-2-(acetylamino)fluorene, was analyzed under conditions of cytosolic sulfonation. Bovine serum albumin did not significantly increase the minimal quantities of the o-(sulfooxy) esters of 1- and 3-hydroxy-2-(benzoylamino)fluorene formed in its absence. However, synthetic sulfonation of N-hydroxy-2-(benzoylamino)fluorene yielded major amounts (85%) of the o-(sulfooxy) esters. These findings indicate that N-(sulfooxy)-2-(benzoylamino)fluorene is unstable and undergoes rapid ortho rearrangement. The evidence suggests that N-hydroxy-2-(benzoylamino)fluorene is a poor substrate for cytosolic sulfonation. It is therefore not a substrate suitable for investigation of the specificity of bovine serum albumin in catalyzing the ortho arrangement of enzymatically generated N-(sulfooxy) esters of arylhydroxyamic acids.
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U2 - 10.1021/tx00020a010
DO - 10.1021/tx00020a010
M3 - Article
C2 - 1782347
AN - SCOPUS:0026021351
SN - 0893-228X
VL - 4
SP - 187
EP - 194
JO - Chemical research in toxicology
JF - Chemical research in toxicology
IS - 2
ER -