Identification of Odoriferous Sulfanylalkanols in Human Axilla Secretions and Their Formation through Cleavage of Cysteine Precursors by a CS Lyase Isolated from Axilla bacteria

Abstract

Human axillary odor is known to be formed upon the action of Corynebacteria sp. on per se odorless axilla secretions. Besides the known odoriferous acids, we report the occurrence in human axilla secretions of four odoriferous sulfanylalkanols, namely 3-sulfanylhexan-1-ol (3), 2-methyl-3-sulfanylbutan-1-ol (4), 3-sulfanylpentan-1-ol (5), and 3-methyl-3-sulfanylhexan-1-ol (6). These compounds have a pungent sweat/kitchen odor, also reminiscent of onions with some fruity connotations, and perception thresholds in the pg/l range. It was postulated that the odorless precursors for these compounds are cysteine conjugates. Bacterial isolates obtained from the human axilla and belonging to the Corynebacteria were, indeed, found to have the enzymatic capacity to release various thiols from cysteine conjugates. The metC gene, which is known to code for a cystathione-beta-lyase, was cloned from the axilla isolate Corynebacterium striatum Ax20 and heterologously expressed in E. coli. The pure recombinant enzyme cleaves various cysteine conjugates and has a similar substrate specificity as the cell homogenates of the wild-type. The recombinant enzyme was finally incubated with odorless axilla secretions and shown to release odoriferous thiols.

Body odour of monozygotic human twins: a common pattern of odorant carboxylic acids released by a bacterial aminoacylase from axilla secretions contributing to an inherited body odour type

“…As observed previously (Shelley et al 1953;Troccaz et al 2004;Natsch et al 2006), both the concentrated hexane fraction and the concentrated aqueous fraction of sweat samples obtained by physical exercise had only a faint odour, which is in line with the well-established notion that odour is only released by bacterial action (Shelley et al 1953). Within a pooled hexane fraction, a large number of components were identified by routine database comparison, but the 25 most abundant peaks appear either to be exogenous (especially fragrance components, emollients used in cosmetics, plasticizers and antioxidants) or they are simple fatty acids (C14-C18, saturated and unsaturated) and squalene, compounds generally present in the skin.…”

“…We had shown that most of these acids are odorants and that they occur in different ratios on different individuals, but whether these ratios are stable over time and whether they are genetically fixed had not been investigated. Finally, different sulfanylalkanols have been reported by several authors as further odour components in axilla secretions (Hasegawa et al 2004;Natsch et al 2004;Troccaz et al 2004). Interestingly, these specific human body odorants were not detected at all in the analytical population studies summarized above addressing the question of an individual-specific odour type (Curran et al 2005;Penn et al 2007).…”

“…The synthesis of reference compounds has been described before (Natsch et al 2003(Natsch et al , 2006.…”

“…For a first analytical inventory, a pool with aliquots of all aqueous samples was split in two and one half was treated with the specific N a -acyl-glutamine-aminoacylase whereas the other was left untreated. The untreated sample had only a faint, acidic odour, whereas the pooled, enzyme-treated sample developed a very pungent, typical axilla odour as observed before (Natsch et al 2006). The two samples were compared after methyl ester formation by comprehensive GC!GC-ToF-MS.…”

“…They reported that (E )-3-methyl-2-hexenoic acid is the key odour component but they also found several other carboxylic acids. In our previous work (Natsch et al 2006), we had identified a series of 26 different carboxylic acids in axilla secretions, which are secreted as N a -acyl-glutamine-conjugates and which are released from these conjugates by the enzyme N a -acyl-glutamineaminoacylase (N-AGA) isolated from commensal skin bacteria inhabiting the human axilla (Natsch et al 2003(Natsch et al , 2006. We had shown that most of these acids are odorants and that they occur in different ratios on different individuals, but whether these ratios are stable over time and whether they are genetically fixed had not been investigated.…”