Abstract
Human body odour is dominated by the scent of specific odourants emanating from specialized glands in the axillary region. These specific odourants are produced by an intricate interplay between biochemical pathways in the host and odour-releasing enzymes present in commensal microorganisms of the axillary microbiome. Key biochemical steps for the release of highly odouriferous carboxylic acids and sulfur compounds have been elucidated over the past 15 years. Based on the profound molecular understanding and specific analytical methods developed, evolutionary questions could be asked for the first time with small population studies: (i) a genetic basis for body odour could be shown with a twin study, (ii) no effect of genes in the human leukocyte antigen complex on the pattern of odourant carboxylic acid was found, and (iii) loss of odour precursor secretion by a mutation in the ABCC11 gene could explain why a large fraction of the population in the Far East lack body odour formation. This review summarizes what is currently known at the molecular level on the biochemistry of the formation of key odourants in the human axilla. At the same time, we present for the first time the crystal structure of the Nα-acyl-aminoacylase, a key human odour-releasing enzyme, thus describing at the molecular level how bacteria on the skin surface have adapted their enzyme to the specific substrates secreted by the human host.This article is part of the Theo Murphy meeting issue ‘Olfactory communication in humans’.
Highlights
The human axillary skin region has long been recognized as an important scent organ
The axillary skin is covered by a dense array of glands [1], and at the same time, this skin niche is colonized by a large population of bacteria [2,3]
We present for the first time the crystal structure of the key enzyme involved in body odour release
Summary
The human axillary skin region has long been recognized as an important scent organ. The axillary skin is covered by a dense array of glands [1], and at the same time, this skin niche is colonized by a large population of bacteria [2,3]. The skin glands secrete specific odourless precursor molecules, and the action of bacterial enzymes triggers the release of the volatile odourants from these precursors. This complex interplay has been investigated at the molecular level in great detail over the past 15 years. We summarize what is currently known on the biochemistry, focusing on both the glands of the host and the enzymes of the bacterial commensals. The findings are integrated and discussed in relation to the role that axillary odour may have had in our evolutionary history and how coevolution shaped the enzymatic capacity of our commensal microorganisms on the skin
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