Key Enzyme behind Human Underarm Malodor Identified
A team of researchers from the University of York, the University of St Andrews and Unilever RD has discovered a unique enzyme responsible for the characteristic human odor.
Overview of bacterial biotransformation of the odorless physiological malodor precursor Cys-Gly-3M3SH, which is secreted onto the surface of skin by underarm apocrine glands, subcutaneously located in the hypodermis. In Staphylococcus hominis, Cys-Gly-3M3SH is actively transported by the di-/tri-peptide transporter (DtpT) along with the movement of protons (1). Once inside the cell the terminal glycine is cleaved by a dipeptidase (PepA) to release Cys-3M3SH (2), which is metabolized by a C-S β-lyase liberating volatile 3M3SH (3), which diffuses or is exported out of the cell (4). The catabolism of Cys-Gly-3M3SH provides carbon and nitrogen as nutritional incentive in the form of glycine, ammonia and pyruvate. Image credit: Rudden et al, doi: 10.1038/s41598-020-68860-z.
Body odor is a characteristic trait of Homo sapiens, however its role in human behavior and evolution is poorly understood.
It is produced by bacterial transformation of odorless molecules secreted onto the surface of the skin by apocrine glands, one of two major types of sweat gland found in humans.
These glands open into hair follicles and typically occur in high density at specific body sites (underarm, nipple and external genitalia).
Commensal microbes, such as Staphylococcus, Cutibacterium and Corynebacterium, are known to play an important role in the generation of the human body odor.
University of York’s Professor Gavin Thomas and colleagues previously identified three odor-forming species of staphylococci: Staphylococcus hominis, Staphylococcus haemolyticus and Staphylococcus lugdunensis.
In the new study, the researchers discovered a unique enzyme found only within these bacteria and responsible for the characteristic underarm malodor.
“Solving the structure of this ‘body odor enzyme’ has allowed us to pinpoint the molecular step inside certain bacteria that makes the odor molecules,” said co-first author Dr. Michelle Rudden, a scientist in the Department of Biology at the University of York.
“This is a key advancement in understanding how body odor works, and will enable the development of targeted inhibitors that stop body odor production at source without disrupting the underarm microbiome.”
The study authors also demonstrated that odor-forming staphylococci appeared approximately 60 million years ago.
“The ‘body odor enzyme’ was present in Staphylococcus hominis long before the emergence of Homo sapiens as a species,” they said.
“Thus the body odor existed prior to the evolution of modern humans, and may have had an important role in societal communication among ancestral primates.”
The team’s paper was published this week in the journal Scientific Reports.
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M. Rudden et al. 2020. The molecular basis of thioalcohol production in human body odour. Sci Rep 10, 12500; doi: 10.1038/s41598-020-68860-z
