Enzyme kinetics dual-substrate reactions

It is not always immediately apparent from an enzymatic reaction whether it should be treated with single- or dual-substrate enzyme kinetic expressions. Lactose hydrolase, which catalyzes the hydrolysis of lactose according to... 

The first synthetic bisubstrate analog inhibitor 18 was successfully designed for al,2-FucT II by Palcic et al., based on the proposed ion-pair mechanism shown in Scheme 8 [22]. Analog 18, where the Gal unit is attached to the terminal phosfor of GDP through a flexible ethylene linkage, was found to be a competitive inhibitor with respect to both donor and acceptor substrates with K values of 16 and 2.3 pM, respectively. Inhibition studies with the bisubstrate analog also helped establish the kinetic mechanism of the enzyme reaction. These dual competitive inhibition patterns are only consistent with a random kinetic mechanism where either substrate can bind to free enzyme. 

---