2-Acetylaminofluorene (AAF, 2-AAF) is a

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

and

mutagenic In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in ...

derivative of fluorene. It is used as a biochemical tool in the study of

carcinogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abnor ...

. It induces

tumors A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

in a number of species in the liver, bladder and kidney. The metabolism of this compound in the body by means of

biotransformation Biotransformation is the biochemical modification of one chemical compound or a mixture of chemical compounds. Biotransformations can be conducted with whole cells, their lysates, or purified enzymes. Increasingly, biotransformations are effected w ...

reactions is the key to its

carcinogenicity A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

. 2-AAF is a substrate for

cytochrome P-450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compo ...

(CYP) enzyme, which is a part of a super family found in almost all organisms. This reaction results in the formation of

hydroxyacetylaminofluorene Hydroxyacetylaminofluorene is a derivative of 2-acetylaminofluorene used as a biochemical tool in the study of carcinogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are ...

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 (NAT) is an enzyme that catalyzes the transfer of acetyl groups from acetyl-CoA to arylamines, arylhydroxylamines and arylhydrazines. They have wide specificity for aromatic amines, particularly serotonin, and can also catal ...

enzyme to yield ''N''-acetyl-''N''-acetoxyaminofluorene. This intermediate can spontaneously rearrange to form the arylamidonium ion and a

carbonium In chemistry, a carbonium ion is any cation that has a pentavalent carbon atom. The name carbonium may also be used for the simplest member of the class, properly called methanium (), where the five valences are filled with hydrogen atoms. The nex ...

ion which can interact directly with DNA to produce DNA adducts. In addition to

esterification In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

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 In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

groups in DNA, proteins and endogenous

thiols In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

glutathione Glutathione (GSH, ) is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, pero ...

. Other metabolites such as the ''N'',''O''-

glucuronide A glucuronide, also known as glucuronoside, is any substance produced by linking glucuronic acid to another substance via a glycosidic bond. The glucuronides belong to the glycosides. Glucuronidation, the conversion of chemical compounds to glucur ...

, 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.

References

{{DEFAULTSORT:Acetylaminofluorene, 2- Carcinogens Acetamides

See also

References