Temperature: increasing the temp. will increase the reaction rate of any reaction
pH of solution: also effects the shape of the enzyme by changing the interactions of charges on the acidic (- charge) and basic (+ charge) amino acids.
Number of substrate and/or enzyme molecules available: the amount of workers vs. materials and vice versa. Presence of inhibitors: Competitive - action at the active site, similar molecules in shape
Non-competitive / allosteric - ('other' 'shape')