2-Acetylaminofluorene
Encyclopedia
2-Acetylaminofluorene is a carcinogenic and mutagenic derivative of fluorene
. It is used as a biochemical tool in the study of carcinogenesis
. It induces tumors in a number of species in the liver, bladder and kidney.The metabolism of this compound in the body by means of biotransformation
reactions is the key to its carcinogenicity. 2-AAF is a substrate for cytochrome P-450 (CYP) enzyme, which is a part of a super family found in almost all organisms. This reaction results in the formation of N-hydroxy-2-acetylaminofluorene
which is a proximal carcinogen and is more potent than the parent molecule. The N-hydroxy metabolite undergoes several enzymatic and non-enzymatic rearrangements. It can be O-acetylated by cytosolic N-acetyltransferase
enzyme to yield N-acetyl-N-acetoxyaminofluorene
. This intermediate can spontaneously rearrange to form the arylamidonium ion and a carbonium ion which can interact directly with DNA to produce DNA adducts. In addition to esterification by acetylation, the N-hydroxy derivative can be O-sulfated by cytosolic sulfur transferase enzyme giving rise to the N-acetyl-N-sulfoxy product.
In addition, the cytosolic N,O-aryl hydroxamic acid acyltransferase enzyme catalyzes the transfer of the acetyl group from the N atom of the N-OH-2-AAF to the O atom of the N-OH group to produce N-acetoxy-2-aminofluorene (N-OH-2-AF). This reactive metabolite spontaneously decomposes to form a nitrenium ion which will also react with DNA. However, the product of this latter reaction is the deacetylated aminofluorene adduct. The interconversion of amide and amine metabolites of 2-AAF can further occur via the microsomal enzyme deacetylase producing the N-hydroxy metabolite of the amine derivative. Subsequent esterification of the aryl hydroxylamine by sulfur transferase yields the sulfate ester which also spontaneously decompose to form nitrenium ion. The reactive nitrenium, carbonium and arylamidonium ion metabolites of 2-AAF react with the nucleophilic groups in DNA, proteins and endogenous thiols like glutathione
. Other metabolites such as the N,O-glucuronide
, although not directly activated products, can be important in the carcinogenic process because they are capable of degradation to proximal N-hydroxy metabolites. This metabolite is presumed to be involved in formation of bladder tumors. The mechanism for this is thought to involve degradation of glucuronide in the bladder due to acidic pH of urine.
Fluorene
Fluorene, or 9H-fluorene, is a polycyclic aromatic hydrocarbon. It forms white crystals that exhibit a characteristic, aromatic odor similar to that of naphthalene. It is combustible. It has a violet fluorescence, hence its name. For commercial purposes it is obtained from coal tar...
. It is used as a biochemical tool in the study of carcinogenesis
Carcinogenesis
Carcinogenesis or oncogenesis is literally the creation of cancer. It is a process by which normal cells are transformed into cancer cells...
. It induces tumors in a number of species in the liver, bladder and kidney.The metabolism of this compound in the body by means of biotransformation
Biotransformation
Biotransformation is the chemical modification made by an organism on a chemical compound. If this modification ends in mineral compounds like CO2, NH4+, or H2O, the biotransformation is called mineralisation....
reactions is the key to its carcinogenicity. 2-AAF is a substrate for cytochrome P-450 (CYP) enzyme, which is a part of a super family found in almost all organisms. This reaction results in the formation of N-hydroxy-2-acetylaminofluorene
Hydroxyacetylaminofluorene
Hydroxyacetylaminofluorene is a derivative of 2-acetylaminofluorene used as a biochemical tool in the study of carcinogenesis....
which is a proximal carcinogen and is more potent than the parent molecule. The N-hydroxy metabolite undergoes several enzymatic and non-enzymatic rearrangements. It can be O-acetylated by cytosolic N-acetyltransferase
N-Acetyltransferase
N-acetyltransferase is an enzyme that catalyzes the transfer of acetyl groups from acetyl-CoA to arylamines. They have wide specificity for aromatic amines, particularly serotonin, and can also catalyze acetyl transfer between arylamines without CoA. EC 2.3.1.5....
enzyme to yield N-acetyl-N-acetoxyaminofluorene
Acetoxyacetylaminofluorene
Acetoxyacetylaminofluorene is a derivative of 2-acetylaminofluorene used as a biochemical tool in the study of carcinogenesis. It forms adducts with DNA by reacting with guanine at its C-8 position.; This results in breaks in one strand of the DNA....
. This intermediate can spontaneously rearrange to form the arylamidonium ion and a carbonium ion which can interact directly with DNA to produce DNA adducts. In addition to esterification by acetylation, the N-hydroxy derivative can be O-sulfated by cytosolic sulfur transferase enzyme giving rise to the N-acetyl-N-sulfoxy product.
In addition, the cytosolic N,O-aryl hydroxamic acid acyltransferase enzyme catalyzes the transfer of the acetyl group from the N atom of the N-OH-2-AAF to the O atom of the N-OH group to produce N-acetoxy-2-aminofluorene (N-OH-2-AF). This reactive metabolite spontaneously decomposes to form a nitrenium ion which will also react with DNA. However, the product of this latter reaction is the deacetylated aminofluorene adduct. The interconversion of amide and amine metabolites of 2-AAF can further occur via the microsomal enzyme deacetylase producing the N-hydroxy metabolite of the amine derivative. Subsequent esterification of the aryl hydroxylamine by sulfur transferase yields the sulfate ester which also spontaneously decompose to form nitrenium ion. The reactive nitrenium, carbonium and arylamidonium ion metabolites of 2-AAF react with the nucleophilic groups in DNA, proteins and endogenous thiols like glutathione
Glutathione
Glutathione is a tripeptide that contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side-chain...
. Other metabolites such as the N,O-glucuronide
Glucuronide
A glucuronide, also known as glucuronoside, is any substance produced by linking glucuronic acid to another substance via a glycosidic bond...
, although not directly activated products, can be important in the carcinogenic process because they are capable of degradation to proximal N-hydroxy metabolites. This metabolite is presumed to be involved in formation of bladder tumors. The mechanism for this is thought to involve degradation of glucuronide in the bladder due to acidic pH of urine.