 Enzymes aren’t used up  Enzymes are not changed by the reaction  Re-used again for the same reaction with other molecules.  Most enzymes are proteins (tertiary and quaternary structures)  Act as catalyst to accelerates a reaction  Are specific for what they will catalyze

Enzyme may be used again Enzyme-substrate complex E S P E E P Reaction coordinate © 2007 Paul Billiet ODWSODWS

 Enzymes can increase the rate of reactions without increasing the temperature.  They do this by lowering the activation energy.

 Substrate concentration  PH  Temperature  Inhibitors

The increase in velocity is proportional to the substrate concentration Reaction velocity Substrate concentration © 2007 Paul Billiet ODWSODWS

Faster reaction but it reaches a saturation point when all the enzyme molecules are occupied. Vmax Reaction velocity Substrate concentration V max © 2007 Paul Billiet ODWSODWS

Extreme pH levels will produce denaturation – Most human enzymes = PH 6-8 depends on it’s location in the body pepsin (stomach) = pH 3 trypsin (small intestines) = pH 8 The structure of the enzyme is changed The active site is distorted and the substrate molecules will no longer fit in it

Enzyme activity Trypsin Pepsin pH

Effect on rates of enzyme activity – Optimum temperature human enzymes – 35°- 40°C (body temp = 37°C) – Raise temperature (boiling) denature protein unfold lose shape – Lower temperature T° molecules move slower fewer collisions between enzyme & substrate

 Many are a lot lower, cold water fish will die at 30°C because their enzymes denature  A few bacteria have enzymes very high temperatures up to 100°C  Most enzymes however are fully denatured at 70°C

Michaelis and menten at low substrate concentrations, the enzyme is not saturated with the substrate and the reaction is not proceeding at maximum velocity whereas when the enzyme is saturated with substrate, maximum velocity is observed.

K m : The addition of a competitive inhibitor increases the observed K m for a given substrate. Therefore, in the presence of a competitive inhibitor, more substrate is needed to achieve it. V max : Competitive inhibitors do not alter V max. The effect of a competitive inhibitor is reversed by increasing [S]. high substrate concentration, the reaction velocity reaches the same V max as that observed in the absence of the inhibitor. This is because at the higher concentration the active site will be saturated with substrate which means the inhibitor cannot bind

K m : Non-competitive inhibitors do not interfere with the binding of substrate to enzyme. Thus, the enzyme shows the same K m in the presence or absence of the non-competitive inhibitor. V max : Increasing the concentration of substrate does not overcome non-competitive inhibition. Non-competitive inhibitors therefore decrease the V max of the reaction. Non-competitive inhibitors therefore simply reduce the amount of active enzyme so they decrease V max, but have no effect on K m

Michaelis-Menten Equation

Is a member of the phosphomonoestrases group. Which are highly specific and act on only one substrate, alkaline phosphatase has a broad substrate specificity and is named alkaline phosphatase because its PH optimum is usually around 9 but other broad spectrum phosphoesterases with PH optima less than 7 are termed acid phosphatases.

Enzyme kinetics: the study of the rate at which an enzyme works. To examine it, when the substrate available to the enzyme one would do the following: 1. set up the series of tubes containing graded concentrations of substrate 2.At time zero, a fixed amount of the enzyme preparation is added 3.Over the next few minutes, the concentration of product formed, is measured. If the product absorbs light, we can easily do this in a spectrophotometer 4.Early in the run, when the amount of substrate is in substantial excess to the amount of enzyme, the rate we observed is the initial of velocity Vi.