The factors affecting the enzyme activity are as follows: 

1. Concentration of substrate: 

a. Increase in the substrate concentration gradually increases the velocity of enzyme activity within the limited range of substrate levels. 

b. A rectangular hyperbola is obtained when velocity is plotted against the substrate concentration. 

c. Three distinct phases (A, B and C) of the reaction are observed in the graph. Where V = Measured velocity, V_max = Maximum velocity, S = Substrate concentration, K_m = Michaelis-Menten constant. 

d. K_m or the Michaelis-Menten constant is defined as the substrate concentration (expressed in moles/lit) to produce half of maximum velocity in an enzyme catalyzed reaction.

e. It indicates that half of the enzyme molecules (i.e. 50%) are bound with the substrate molecules when the substrate concentration equals the Km value. 

f. K_m value is a constant and a characteristic feature of a given enzyme. 

g. It is a representative for measuring the strength of ES complex. 

h. A low K value indicates a strong affinity between enzyme and substrate, whereas a high Km value reflects a weak affinity between them. 

i. For majority of enzymes, the K values are in the range of 10_-5 to 10_-2 moles.