Search

An abstract of the article "Hice1, a Novel Microtubule-Associated Protein Required for Maintenance of Spindle Integrity and Chromosomal Stability in Human Cells" by Guikai Wu, Yi-Tzu Lin, and Randy Wei is presented.

Nontoxic natural products useful in skin care cosmetics are of considerable interest. Tyrosinase is a rate-limiting enzyme for which its inhibitor is useful in developing whitening cosmetics. Pyracantha koidzumii (Hayata) Rehder is an endemic species in Taiwan that exhibits tyrosinase-inhibitory activity. To find new active natural compounds from P. koidzumii, we performed bioguided isolation and studied the related activity in human epidermal melanocytes. In total, 13 compounds were identified from P. koidzumii in the present study, including two new compounds, 3,6-dihydroxy-2,4-dimethoxy-dibenzofuran (9) and 3,4-dihydroxy-5-methoxybiphenyl-2'-O-β-D-glucopyranoside (13), as well as 11 known compounds. The new compound 13 exhibited maximum potency in inhibiting cellular tyrosinase activity, the protein expression of cellular tyrosinase and tyrosinase-related protein-2, as well as the mRNA expression of Paired box 3 and microphthalmia-associated transcription factor in a concentration-dependent manner. In the enzyme kinetic assay, the new compound 13 acted as an uncompetitive mixed-type inhibitor against the substrate L-3,4-dihydroxyphenylalanine and had a Km value against this substrate of 0.262 mM, as calculated using the Lineweaver-Burk plots. Taken together, our findings show compound 13 exhibits tyrosinase inhibition in human melanocytes and compound 13 may be a potential candidate for use in cosmetics. [ABSTRACT FROM AUTHOR]

Discusses a functional link between ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) gene products. Susceptibility of A-T and NBS to cancer and similar cellular phenotypes; Mutation of NBS1 in patients with Nijmegen breakage syndrome and the formation of a complex with DNA repair proteins; Various testing methods used, including immunoblotting and immunoprecipitation.