Tethered enzymatic reactions are a key component in signalling transduction pathways. It is found that many surface receptors rely on the tethering of cytoplasmic kinase to initiate and integrate signalling. A key factor to such reaction is the molecular reach; however, the role of it is incompletely understood. To date, a large number of compartment-based ODE and stochastic models have been developed to study this problem. In recent years, spatial-stochastic models have emerged as a more realistic representation for such processes, among which lattice-based stochastic reaction-diffusion models are a popular approach for studying complex spatio-temporal processes inside cells. To understand the role of molecular reach in tethered signalling, we employed an accurate and convergent lattice-based stochastic reaction-diffusion model (CRDME). We find that the molecular reach can increase or decrease biochemical reactions depending on the diffusion coefficient in 2D membrane but not in 3D cytosol.