Tokyo University of Science Discovery of a compound that exhibits tyrosinase inhibitory activity from bacteria resident on human skin – Contributing to the development of highly safe cosmetic raw materials that suppress melanin production –

Tokyo University of Science
Discovery of a compound that exhibits tyrosinase inhibitory activity from bacteria resident on human skin – Contributing to the development of highly safe cosmetic raw materials that suppress melanin production –
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[Research summary and points]
By inhibiting the activity of tyrosinase, which is deeply involved in melanin production, pigmentation due to melanin accumulation can be prevented.
This time, we have discovered a substance derived from indigenous bacteria on human skin that exhibits tyrosinase inhibitory activity. This is the first report of a resident bacteria on human skin. The newly discovered compound has the potential to be applied as a cosmetic raw material or food additive with low impact on humans and the environment.
[Research overview]
A research group led by Yuka Sekino (1st year master’s student), Assistant Professor Yuki Furuyama, and Professor Koji Kuramochi from the Department of Life and Biological Sciences, Faculty of Advanced Science and Engineering, Tokyo University of Science, conducted research on cyclo(L- We discovered that Pro-L-Tyr) inhibits tyrosinase activity. This is the first report demonstrating that bacteria isolated from human skin exhibit tyrosinase inhibitory activity, and is expected to contribute to the development of cosmetic raw materials and food additives that have less impact on humans and the
environment.
Melanin is produced by pigment cells in the dermis to protect the skin from harmful UV rays. Melanin is shed along with dead epidermal cells every 28 days, but when this cycle is disrupted, such as by aging or exposure to UV rays, pigmentation occurs due to the accumulation of melanin. Various substances have been reported as compounds that inhibit melanin accumulation, but side effects and toxicity can be problematic, so there is a need to develop highly safe melanin production inhibitors.
In this research, we focused on the enzyme tyrosinase, which is deeply involved in melanin production, and searched for compounds with tyrosinase inhibitory activity from bacteria resident on human skin. Since resident skin bacteria grow on the skin without being eliminated by the human immune system, it is thought that they may produce compounds that inhibit tyrosinase activity with low toxicity to humans.
As a result of screening skin-derived bacteria, we found that Corynebacterium tuberculostearicum, a species of Corynebacterium, inhibits tyrosinase activity (Figure 1). Isolation by preparative thin layer chromatography (*1) and structural analysis by nuclear magnetic resonance (NMR) (*2) revealed that the compound with tyrosinase inhibitory activity is cyclo(L-Pro-L-Tyr). Confirmed.
Based on these results, cyclo(L-Pro-L-Tyr) has the potential to be applied to cosmetics and food additives as a highly safe tyrosinase inhibitor compound.
The results of this research were published online in the
international academic journal “International Journal of Molecular Sciences” on July 4, 2024.
*Please note that the PR TIMES system does not allow the use of superscripts, subscripts, special characters, etc., so the notation may differ from the official notation. For the official notation, please refer to the Tokyo University of Science web page
(https://www.tus.ac.jp/today/archive/20240729_7832.html).
[Image 1: https://prtimes.jp/i/102047/92/resize/d102047-92-79224307366d7f0ff531-0.jpg&s3=102047-92-9d37a6ee6ac68c7407e60691864dff17-1500×679.jpg] Figure 1. Overview of this study. We have discovered a substance with tyrosinase inhibitory activity from human skin-derived indigenous bacteria.
[Research background]
Tyrosinase is an important enzyme involved in melanin biosynthesis. L-tyrosine is oxidized to dihydroxyphenylalanine (DOPA) quinone via L-DOPA in a two-step reaction by tyrosinase. DOPAquinone is converted to DOPAchromium through a spontaneous oxidation reaction, which polymerizes to produce melanin.
Tyrosinase inhibitors are used in the cosmetics industry to suppress melanin production induced by UV radiation and aging. Kojic acid, hydroquinone, and glutathione are examples of tyrosinase inhibitors commonly used as cosmetic ingredients. However, some of these compounds can cause serious adverse events. For example, hydroquinone is not recommended for use due to side effects such as vitiligo-like symptoms, redness, and rash. Therefore, there is a need to develop highly safe tyrosinase inhibitors.
In recent years, the approach of searching for candidate substances for tyrosinase inhibitors from compounds derived from microorganisms has become popular. Kojic acid, produced by the fungus Aspergillus oryzae, is a representative example and is attracting attention as a less harmful compound as an alternative to synthetic tyrosinase inhibitors. Bacteria derived from soil and oceans produce a variety of compounds, and in addition to kojic acid, some have been found to exhibit tyrosinase inhibitory activity.
Microorganisms live in countless numbers in our human bodies. Intestinal bacteria are a typical example, but a variety of bacteria also live on the skin. Because these skin-resident bacteria are not targeted by immune responses, the compounds they produce are expected to have low toxicity to the skin. However, tyrosinase inhibitors derived from bacteria resident on the skin have not yet been reported. Therefore, in this study, we searched for tyrosinase inhibitors using bacteria isolated from human skin as a search source.
[Details of research results]
Bacterial strains collected from the skin were randomly selected, cultured, and screened based on tyrosinase inhibitory activity. Tyrosinase activity was evaluated by the amount of DOPA chromium produced from L-DOPA. The results showed that sterile culture supernatant samples significantly inhibited the production of DOPAchromium by tyrosinase. As a result of 16S rRNA base sequence analysis, we found that the strain exhibiting tyrosinase inhibitory activity was C. tuberculostearicum.
Next, to obtain a compound with tyrosinase inhibitory activity from C. tuberculostearicum medium, it was purified using preparative thin layer chromatography. NMR analysis of the purified compound identified it as cyclo(L-Pro-L-Tyr). We also confirmed that purified
cyclo(L-Pro-L-Tyr) actually exhibits tyrosinase inhibitory activity. To determine whether the tyrosine residue of cyclo(L-Pro-L-Tyr) is important for the inhibitory activity, tyrosinase was isolated from two analogues, cyclo(L-Pro-L-Val) and cyclo(L- When treated with Pro-L-Leu), neither of them inhibited tyrosinase activity (Figure 2).
[Image 2: https://prtimes.jp/i/102047/92/resize/d102047-92-b306859c88837b27959c-1.jpg&s3=102047-92-f3bb6705b7e32e2f9c396a8f15966319-676×667.jpg] Figure 2. Absorbance of cyclo(L-Pro-L-Tyr), cyclo(L-Pro-L-Val) and cyclo(L-Pro-L-Leu) at 492 nm (mean ± standard deviation, *** p < 0.001). Shows tyrosinase inhibitory activity.
Finally, in order to estimate the mode of action of
cyclo(L-Pro-L-Tyr), we performed a docking simulation (*3) of tyrosinase and cyclo(L-Pro-L-Tyr). The results suggested that cyclo(L-Pro-L-Tyr) binds to the substrate binding site of tyrosinase and inhibits its activity by closing the substrate pocket (Figure 3).
[Image 3: https://prtimes.jp/i/102047/92/resize/d102047-92-58985f809acf54d63081-2.png&s3=102047-92-b74be635c16d1902d9d2cdb121c86748-1034×720.png ]
Figure 3. Three-dimensional plot of the molecular docking diagram of tyrosinase with L-tyrosine and cyclo (L-Pro-L-Tyr) complexes. Yellow: Tyr, light purple: L-Pro-L-Tyr, blue and green areas:
solvent-accessible surface of tyrosinase. Tyrosinase is indicated by red, gray, cyan, and green ribbons.
Source: Sekino, Yuika, et al. “Cyclo(L-Pro-L-Tyr) isolated from the human skin commensal Corynebacterium tuberculostearicum inhibits tyrosinase.” International Journal of Molecular Sciences, vol. 25, no. 13, July 2024, p .7365
Assistant Professor Furuyama, who led this research, said,
“Cyclo(L-Pro-L-Tyr) is the first tyrosinase inhibitor isolated from a resident human skin bacterium.It is a cosmetic raw material with high safety and low environmental impact. It has the potential to be used in the future as food additives.”
*This research was supported by Grant-in-Aid for Scientific Research (22K14814) from the Japan Society for the Promotion of Science (JSPS). 【term】
*1 Preparative thin layer chromatography
A method of purifying spots developed on a thicker plate than in normal thin layer chromatography (a type of liquid chromatography) by solvent extraction.
*2 Nuclear magnetic resonance (NMR)
A method of analyzing the characteristics of atomic nuclei in a material by irradiating the material with electromagnetic waves while a magnetic field is applied. It is used to determine the structure of compounds and elucidate interactions between molecules.
*3 Docking simulation
A simulation that estimates how molecules such as enzymes and proteins interact. [Paper information]
Magazine name: International Journal of Molecular Sciences
Paper title: Cyclo(L-Pro-L-Tyr) isolated from the human skin commensal Corynebacterium tuberculostearicum inhibits tyrosinase
Author: Yuika Sekino, Ikuya Yamamoto, Masahiro Watanabe, Kouji Kuramochi and Yuuki Furuyama
DOI: 10.3390/ijms25137365
URL: https://doi.org/10.3390/ijms25137365