1 EU is defined as the amount of enzyme that will yield product formation rate of 1 micromole per minute. So it seems that EU has the units of amount (mass or moles), as it's defined as "the amount of enzyme which..." . But in the class they told us that under certain conditions, 1 EU=the reaction rate. So now - EU has the units of rate... for me it's like you would ask me how old am I and I would answer: 55 mph! How is this transition made from the defenition of "amount" to that of "rate"??? what's the math behind it?