In biochemstry, the use of "turnover number" is slightly different- it is the amount of substrate that an enzyme can convert to product per unit time.
Turnover number is notated as kcat. It can be calculated with the formula kcat=Vmax/[E], where [E] is the concentration of enzyme, and Vmax is the maximum rate of conversion (generally found when [S] >>> [E]). kcat has units of inverse seconds (s-1); a certain enzyme that has a kcat value of 10,000 means that each enzyme can convert 10,000 molecules of substrate per second.