Gray hair in old age: Hydrogen peroxide inhibits the formation of melanin
Scientists from Mainz and Bradford cover the molecular mechanism for the gray and white coloring of hair in old age
Gray or white hair arise with increasing years of life by a quite natural process of aging, which has less color pigments are formed.
Scientists at the University of Mainz and the University of Bradford in the UK have now uncovered the secret to the gray or white coloration of hair in old age. Consequently oxygen radicals are major contributors to the loss of hair color. "The starting point of the entire process is hydrogen peroxide, which we also know as a bleaching agent," explains Professor. Dr. Heinz Decker of the Institute of Biophysics at the University of Mainz. "With increasing age there is a greater accumulation in the hair and ultimately inhibits the production of the color pigment melanin." The molecular mechanism of this process have the biophysicists in Mainz for the first time broken accurately along with the dermatologists from Bradford and published in the journal The FASEB Journal.
Hydrogen peroxide - or H2O2 in the chemical name - product of metabolism throughout the human body in small amounts, as well as in the hair. With age, the amount increases, however, because the body does not produce enough with the breakdown of hydrogen peroxide into the two components water and oxygen. In their work, the scientists have shown that an enzyme called catalase for responsible, which normally neutralizes hydrogen peroxide, present in the cells only in very low concentrations. This has dramatic consequences.
Hydrogen peroxide attacks the enzyme tyrosinase by oxidizing a specific block, namely the amino acid methionine. "Through this oxidation process, the function of the enzyme tyrosinase is degraded so much that it can no longer form melanin. We now know the specific molecular dynamic that underlies this process," said Decker. Scientists at the Institute of Biophysics since about ten years working on the research of tyrosinase, which are enzymes present in all organisms and perform many different functions. In the computer simulations to uncover the molecular mechanisms, the biophysicists were supported by the newly established Center for Computational Research Methods in the Natural Sciences at the University of Mainz.
However, the oxidation by hydrogen peroxide paralyzes not only the production of melanin, but also inhibits other enzymes that are needed to restore the damaged proteins. Thus comes a cascade of events in motion, at the end of the gradual loss of pigment throughout the hair - from the hair root to the hair tips - stands. With this work, the researchers from Mainz and Bradford have not only the age-old mystery of why our hair in old age are gray, dissolved at the molecular level, but also approaches for a future therapy as in vitiligo, a skin disorder in the skin, indicated. Because melanin is not only responsible for the coloring of hair, but also the skin and eyes.
The works in Mainz were sponsored by the Collaborative Research Centre 490 "Invasion and persistence of infections" and the Graduate College 1043 "Antigen-specific immunotherapy".
Original publications:
JM Wood, H. Decker, H. Hartmann, B. Chavan, H. Rokos, JD Spencer, S. Hasse, MJ Thornton, M. Shalbaf, R. Paus, and KU Schallreuter Senile hair graying: H2O2-mediated oxidative stress Affects human hair color by blunting methionine sulfoxide repair the FASEB Journal, published online on 23. February 2009, doi: 10.1096 / 08-fj.125435
T. Schweikardt, C. Olivares, F. Solano, E. Jaenicke, JC Garcia Borron and H. Decker A three-dimensional model of mammalian tyrosinase active site accounting for loss of function mutatations Pigment Cell Research (2007) 20: 394- 401
H. Decker, T. Schweikardt and F. Tuczek The first crystal structure of tyrosinase: all questions answered? Angewandte Chemie International Edition Engl, (2006) 45, 4546 -. 4550
Source: Mainz [lei]
