A method for determining the endo or exo enzymatic activity of a test enzyme comprising the following steps: a. Introducing into a liquid medium at least one magnetic or magnetizable or electrically charged particle, said particle floating on the surface of the liquid medium or in suspension in the liquid medium or resting onto an immersed surface in the liquid medium; b. Introducing into said medium a substrate of said test enzyme at a determined concentration; c. Introducing into said medium comprising said substrate said test enzyme; d. Measuring a first degree of freedom of movement of said at least one particle in said medium at a time to corresponding to the introduction of said enzyme into said medium; e. Applying a magnetic or electric or electromagnetic field capable of moving said at least one particle floating on the surface of the culture medium or in suspension in the liquid medium or resting onto an immersed surface in the culture medium for a predetermined time; f. Measuring at least a second degree of freedom of movement of said at least one particle in said medium to a second time t >0 g. Calculating the variation of degree of freedom, ΔDL between the second time t >0 with respect to time to; h. Repeating steps a) to g) with different concentrations of said substrate; i. From a graph obtained with the measured values showing on the abscissa the time values and on the ordinate the values of ΔDL, determining the initial enzymatic speed (v i) in ΔDL per time unit for different substrate concentrations, corresponding to the tangent to the origin of said graph, j. Determine the K ERT constant corresponding to the ability of the enzyme to modify the degree of freedom of movement of said particle in said medium, from a curve obtained with the measured values by making appear on abscissa 1/vi and on ordinate /vi corresponding to the following formula: 1 V i = a × S V i + b where a is the slope of the curve obtained and b is the ordinate at the origin, the K ERT value being equal to the absolute value of the intersection of the curve with the abscissa, k. Comparing the value of the constant K ERT obtained in step i) with a reference constant K ERT obtained from a reference enzyme whose enzymatic activity is previously known for said substrate, said comparison making it possible to determine the endo or exo enzymatic activity of said enzyme. a. Introducing into a liquid medium at least one magnetic or magnetizable or electrically charged particle, said particle floating on the surface of the liquid medium or in suspension in the liquid medium or resting onto an immersed surface in the liquid medium; b. Introducing into said medium a substrate of said test enzyme at a determined concentration; c. Introducing into said medium comprising said substrate said test enzyme; d. Measuring a first degree of freedom of movement of said at least one particle in said medium at a time to corresponding to the introduction of said enzyme into said medium; e. Applying a magnetic or electric or electromagnetic field capable of moving said at least one particle floating on the surface of the culture medium or in suspension in the liquid medium or resting onto an immersed surface in the culture medium for a predetermined time; f. Measuring at least a second degree of freedom of movement of said at least one particle in said medium to a second time t >0 g. Calculating the variation of degree of freedom, ΔDL between the second time t >0 with respect to time to; h. Repeating steps a) to g) with different concentrations of said substrate; i. From a graph obtained with the measured values showing on the abscissa the time values and on the ordinate the values of ΔDL, determining the initial enzymatic speed (v i) in ΔDL per time unit for different substrate concentrations, corresponding to the tangent to the origin of said graph, j. Determine the K ERT constant corresponding to the ability of the enzyme to modify the degree of freedom of movement of said particle in said medium, from a curve obtained with the measured values by making appear on abscissa 1/vi and on ordinate /vi corresponding to the following formula: 1 V i = a × S V i + b where a is the slope of the curve obtained and b is the ordinate at the origin, the K ERT value being equal to the absolute value of the intersection of the curve with the abscissa, k. Comparing the value of the constant K ERT obtained in step i) with a reference constant K ERT obtained from a reference enzyme whose enzymatic activity is previously known for said substrate, said comparison making it possible to determine the endo or exo enzymatic activity of said enzyme.