The *turnover number* for your enzyme is #"90.9 min"^(-1)#.

The turnover number, or #K_"cat"#, expresses how many substrate molecules are converted to product by the enzyme *per unit time*. Moreover, the turnover number is calculated when the enzyme has maximum efficiency #-># #V_"max"#.

#K_"cat" = V_"max"/([E])#, where

#[E]# - the total concentration of enzyme present.

Since #V_"max"# uses #mu"mol"# and the concentration of the enzyme is given in #"nmol"#, I'll convert the latter to #mu"mol"#

#121cancel("nmol") * (10^(-3)mu"mol")/(1cancel("nmol")) = 121 * 10^(-3)mu"mol"#

Once again, plug and play

#K_"cat" = (11.0cancel(mu"mol") * "min"^(-1))/(121 * 10^(-3)cancel(mu"mol")) = "90.9 min"^(-1)#