A human axillary odorant is carried by apolipoprotein D.

Abstract

The characterization of the source of the odor in the human axillary region is not only of commercial interest but is also important biologically because axillary extracts can alter the length and timing of the female menstrual cycle. In males, the most abundant odor component is known to be E-3-methyl-2-hexenoic acid (E-3M2H), which is liberated from nonodorous apocrine secretions by axillary microorganisms. Recently, it was found that in the apocrine gland secretions, 3M2H is carried to the skin surface bound to two proteins, apocrine secretion odor-binding proteins 1 and 2 (ASOBI and ASOB2) with apparent molecular masses of 45 kDa and 26 kDa, respectively. To better understand the formation of axillary odors and the structural relationship between 3M2H and its carrier protein, the amino acid sequence and glycosylation pattern of ASOB2 were determined by mass spectrometry. Axillary secretions and odors are derived from an area of the body with exceptional odor-producing capabilities. Several types of skin glands, including apocrine, eccrine, sebaceous, and apoeccrine glands, contribute moisture and substrate to a large permanent population of cutaneous microflora (9). These consist of lipophilic and large colony diptheroids as well as micrococci. These microorganisms generate a variety of odoriferous compounds that characterize the axillary region. In vivo correlations of odor quality and axillary bacterial populations have demonstrated that the aerobic diptheroids are associated with the stronger, more distinct axillary odor (9).A number of investigations of axillary constituents have focused upon the interesting steroidal molecules found there (10, 11). Volatile odoriferous steroids such as 5a-androst-16-en-313-ol (androstenol) and 5a-androst-16-en-3-one (androstenone) as well as nonvolatile steroid sulfates were identified and quantitated by radioimmunoassay and gas chromatography/mass spectrometry (GC/MS) (10,11), The urine/muskylike odors of androstenone and androstenol were thought by some investigators to be suggestive of axillary odor (9-11). However, recent studies (12, 13) have presented both organoleptic and analytical evidence that a mixture of C6-C11, straight-chain, branched, and unsaturated acids constitute the characteristic axillary odor. In combined male samples, the E-isomer of 3-methyl-2-hexenoic acid (3M2H) is the dominant analytical component of the mixture, while in combined female samples the straight-chain acids are present in greater relative abundance (14). The Z-isomer is also present in both genders, however in different relative abundance: 10:1 (E/Z) in males (12) and 16:1 (E/Z) in females (14).More than 30 years ago, it was demonstrated that the odorless precursors of axillary odor are present in apocrine gland secretions and that the characteristic odor arises from interaction of the odorless apocrine secretion precursors with the axillary microflora (15). The water-soluble components of apocrine secretion were found to contain the odorless precursors of the characterist...

Facts, fallacies, fears, and frustrations with human pheromones

“…Further, no androstenone was detected in these extracts. A related steroid, androstenol, was present (3.5 ng/ l extract), albeit in far lower concentration than E-3M2H (150 ng/ l extract) or the other acids (Zeng et al, 1996b). The Z-isomer of 3M2H was also present in the extracts from each gender, but in different relative abundance: 10:1 (E:Z) in males and 16:1 (E:Z) in females.…”

“…In terms of relative abundance, these acids, in particular (E)-3-methyl-2-hexenoic (E-3M2H), are present in far greater quantity than volatile steroids, e.g., androstenone, which were previously thought to be important axillary odors (Gower and Ruparelia, 1993). In samples of secretions from the axillae of males that were combined before analysis, the concentration of E-3M2H was approximately 357 ng/ l extract, whereas that of androstenone was 0.5 ng/ l extract (Zeng et al, 1996b). In combined samples from females, the straight-chain acids were present in greater relative abundance than E-3M2H.…”

“…The Z-isomer of 3M2H was also present in the extracts from each gender, but in different relative abundance: 10:1 (E:Z) in males and 16:1 (E:Z) in females. E-3M2H and androstenone have comparable low olfactory thresholds (Baydar et al, 1992;Gower and Ruparelia, 1993;Wysocki et al, 1993;Zeng et al, 1996b).…”

“…The precursors to axillary odor reside in the apocrine glands (Labows et al, 1982;Zeng et al, 1992Zeng et al, , 1996aZeng et al, , 1996b. The characteristic axillary odor is formed from the interaction of odorless (water-soluble) precursor molecules found in apocrine secretion with the cutaneous axillary microorganisms (Labows et al, 1982;Zeng et al, 1992).…”

Virtual two‐dimensional gel electrophoresis of high‐density lipoproteins

“…and migrating as though sized between 27000-32000 Da. Glycosylated apolipoprotein D from plasma and axillary extracts has been characterized [17,50]. Based on the mass-analyzed peptides encompassing N-linked glycosylated residues Asn 45 and Asn 78 [17], it was possible to calculate minimum, major, and maximum masses for plasma apoD as 23340, 24287, and 25966, respectively.…”