This step might involve acid-base catalysis by the active-site cysteinyl thiolate (which could explain an effect of the second cysteinyl residue), and/or the conserved lysine residue, yielding GS in analogy to glutathione transferases (Fig
This finding was in good accordance with the literature, where the hydroquinone is routinely shown to auto-oxidate under these conditions 30,31
This clear distinction is indicated on the labels of research chemicals, exempting them from specific regulations under Title 21, Parts 100-740 of the Code of Federal Regulations (21CFR)
FDA routinely conducts similar, web-based inspections, which are well suited to reveal a products intended use often the determining factor in whether a product is a drug. See 21 CFR 201.128 (intended use can be derived from a broad array of objective factors, including labeling claims, advertising matter, or oral or written statements.) See also 21 USC 321(g) (defining drug based on, inter alia, its intended use)
Skin cell turnover takes 4-6 weeks biologically, and melanin distribution changes gradually as new cells replace old ones
Chien KJ, Horng CT, Huang YS, Hsieh YH, Wang CJ, Yang JS, et al