LIFE SCIENCE
'(<a href="http://www.j-archive.com/media/2006-07-10_DJ_30.jpg" target="_blank">Jon of the Clue Crew cuts a dashing figure in his lab coat.</a>)  The reaction that makes human skin tan & the reaction that turns a <a href="http://www.j-archive.com/media/2006-07-10_DJ_30a.jpg" target="_blank">cut fruit brown</a> are catalyzed by the same one of these, called tyrosinase'
an enzyme