<prompt> Enzyme activity is expressed as: PGI Dec 2006MillimoleslitMglitMgdlMicromolesmin  <response>: Ans: D Micromolesmin Enzme activity is expressed as micromoles of substrate converted to product per minute under optical condition of measurement. One standard unit or international unit of enzyme activity U is that activity which catalyses transformation of 1 micromole of substrate per minute.Modern method of enzyme activity is in katals Kat1 KatConversion of 1 mole of substrate per second. 