Final answer:
It is usually easier to calculate an enzyme's reaction velocity from the rate of appearance of product rather than the rate of disappearance of a substrate. Enzyme activity is measured as an initial reaction velocity, the velocity before much substrate has been depleted and before much product has been generated. It is easier to measure the appearance of a small amount of product from a baseline of zero concentration than to measure the disappearance of small amount of substrate against a background of high concentration of substrate.
The rate of appearance of the product is generally easier to measure for calculating enzyme reaction velocity than the rate of disappearance of the substrate. Initial reaction velocity is used to estimate the kinetic properties of enzymes, key for understanding and diagnosing metabolic disorders.
Step-by-step explanation:
During steady-state enzyme kinetics experiments, the enzyme concentration is held constant while the reaction rate is measured at varying substrate concentrations. This is done to generate a Michaelis-Menten plot, which illustrates how the reaction velocity depends on the substrate concentration. The initial reaction rate, or initial velocity (vo), at each substrate concentration can be estimated by plotting the slope of the first few time points on the graph.
Understanding the kinetic properties of enzymes, such as the Km (the substrate concentration at which the reaction rate is half of Vmax) and the maximum rate (Vmax) of the catalyzed reaction, is important for determining the standard rate-limiting reaction in biochemical pathways. The exact measurement of enzyme activity is crucial for diagnosing conditions related to abnormal metabolite production in patients.