2022_11_16_sem_-_alkaline_phosphatase

Introduction to Alkaline Phosphatase

The focus of this note is on Alkaline Phosphatase (ALP) in human biochemistry, presented by Dr. Brigitte A. Graf. The key concepts covered include the determination of enzyme activity, the effect of substrate concentration on enzyme activity, an introduction to Michaelis-Menten kinetics and the Lineweaver-Burk plot, and an examination of enzyme inhibition. The underlying research question investigates whether the enzyme activity of alkaline phosphatase is enhanced or inhibited by the addition of phenyl phosphate (PPP).

Definitions and Context

In the context of enzymes, the suffix "ase" denotes an enzyme, while "phosphatase" specifically refers to enzymes that remove a phosphate group from their substrates. Alkaline Phosphatase functions optimally in alkaline environments, and it holds significant importance as it is commonly found in tissues such as the liver and bones. High levels of ALP often indicate possible liver damage.

Measuring Enzyme Activity

Enzyme activity is measured as the rate of reaction, expressed in mg/mL per minute based on the amount of substrate converted over time. This measurement is crucial as it encompasses the determination of enzyme activity, effects of substrate concentration, and foundational kinetics concepts.

Substrate Concentration Effects

The relationship between substrate concentration (designated as [S]) and the reaction rate (v0) of alkaline phosphatase activity is discussed over several pages. Key concepts include the determination of enzyme activity and a thorough analysis of how substrate concentration influences enzyme activity through kinetic principles.

Michaelis-Menten Equation

The core equation of the Michaelis-Menten model correlates the velocity of the reaction (V0) with substrate concentration ([S]), with the rate of reaction described in moles per second. This equation is essential for understanding enzyme kinetics in a biochemical context.

Vmax and Km Parameters

Vmax represents the maximum velocity of the enzyme-catalyzed reaction, while Km indicates the substrate concentration at which the reaction velocity reaches half of Vmax. High Km values signify low enzyme-substrate (E-S) affinity, whereas low Km values indicate high E-S affinity.

Strategy for High vs Low Km Enzyme Selection

The practical application of this knowledge involves selecting the appropriate enzyme based on substrate cost and reaction efficiency, particularly when comparing enzymes A and B that catalyze the same reaction.

Developing Km Value

The discussion encompasses the challenges associated with accurately determining the Km value for specific enzymes during experiments.

Enzyme Activators

Although not detailed, there is a brief mention of the role of activators, which are substances that can increase enzyme activity.

Enzyme Inhibition Mechanisms

The note outlines various types of enzyme inhibition, elaborating on the interaction pathways where inhibitors can bind either to the enzyme (E) or the enzyme-substrate complex (ES). Key concepts regarding inhibition mechanisms are illustrated through equations demonstrating the transition of substrates and products in enzyme reactions.