{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,24]],"date-time":"2026-06-24T17:15:38Z","timestamp":1782321338898,"version":"3.54.5"},"reference-count":29,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,13]],"date-time":"2021-01-13T00:00:00Z","timestamp":1610496000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Intramural Program, National Eye Institute","award":["ZIA EY000476-10"],"award-info":[{"award-number":["ZIA EY000476-10"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Human Tyrosinase (Tyr) is the rate-limiting enzyme of the melanogenesis pathway. Tyr catalyzes the oxidation of the substrate L-DOPA into dopachrome and melanin. Currently, the characterization of dopachrome-related products is difficult due to the absence of a simple way to partition dopachrome from protein fraction. Here, we immobilize catalytically pure recombinant human Tyr domain (residues 19\u2013469) containing 6xHis tag to Ni-loaded magnetic beads (MB). Transmission electron microscopy revealed Tyr-MB were within limits of 168.2 \u00b1 24.4 nm while the dark-brown melanin images showed single and polymerized melanin with a diameter of 121.4 \u00b1 18.1 nm. Using Hill kinetics, we show that Tyr-MB has a catalytic activity similar to that of intact Tyr. The diphenol oxidase reactions of L-DOPA show an increase of dopachrome formation with the number of MB and with temperature. At 50 \u00b0C, Tyr-MB shows some residual catalytic activity suggesting that the immobilized Tyr has increased protein stability. In contrast, under 37 \u00b0C, the dopachrome product, which is isolated from Tyr-MB particles, shows that dopachrome has an orange-brown color that is different from the color of the mixture of L-DOPA, Tyr, and dopachrome. In the future, Tyr-MB could be used for large-scale productions of dopachrome and melanin-related products and finding a treatment for oculocutaneous albinism-inherited diseases.<\/jats:p>","DOI":"10.3390\/ijms22020734","type":"journal-article","created":{"date-parts":[[2021,1,13]],"date-time":"2021-01-13T11:52:32Z","timestamp":1610538752000},"page":"734","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":28,"title":["Tyrosinase Nanoparticles: Understanding the Melanogenesis Pathway by Isolating the Products of Tyrosinase Enzymatic Reaction"],"prefix":"10.3390","volume":"22","author":[{"given":"Paul K.","family":"Varghese","sequence":"first","affiliation":[{"name":"National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4047-1232","authenticated-orcid":false,"given":"Mones","family":"Abu-Asab","sequence":"additional","affiliation":[{"name":"National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emilios K.","family":"Dimitriadis","sequence":"additional","affiliation":[{"name":"NIH Shared Resources on Biomedical Engineering and Physical Science, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Monika B.","family":"Dolinska","sequence":"additional","affiliation":[{"name":"National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"George P.","family":"Morcos","sequence":"additional","affiliation":[{"name":"National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7204-6572","authenticated-orcid":false,"given":"Yuri V.","family":"Sergeev","sequence":"additional","affiliation":[{"name":"National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1186\/1750-1172-2-43","article-title":"Oculocutaneous albinism","volume":"2","author":"Gronskov","year":"2007","journal-title":"Orphanet J. 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